Gustav Schubert

I have a strange problem with FMX TListbox and the OnClick handler, but apparrently only on my Surface tablet. Cannot reproduce on another machine. Initially I thought it was a strange HDPI related issue, now I think it may be 'just' a driver issue. The first comment contains the test program. It would be interesting if someone can reproduce. Details in comments below. I'm sorry if this turns out to be noise. Symptoms: If I click on a ListBox item then ItemIndex in ListboxClick is wrong, it contains the index of the previously clicked item.

I have applied info from "Patch a private virtual method" topic. My fix as a patch in a minimal test project: unit Unit1; interface uses System.SysUtils, System.Types, System.UITypes, System.Classes, FMX.Types, FMX.Controls, FMX.Forms, FMX.Controls.Presentation, FMX.ListBox; type TForm1 = class(TForm) procedure FormCreate(Sender: TObject); private LB: TListBox; SC: TListBoxSelector; function GetVirtualMethodIndex: Integer; procedure DoOnIdle(Sender: TObject; var Done: Boolean); procedure PatchMouseSelectFinish; protected procedure InspectVMT(const AMethodName: string); end; var Form1: TForm1; implementation {$R *.fmx} uses Windows, System.Rtti; const MSF_MethodName = 'MouseSelectFinish'; type TListBoxAccess = class(TListBox); TMouseSelectProc = procedure( const Item: TListBoxItem; const Button: TMouseButton; const Shift: TShiftState) of object; procedure FixedMouseSelectFinish(Self: TListBoxSelector; const Item: TListBoxItem; const Button: TMouseButton; const Shift: TShiftState); begin if Button <> TMouseButton.mbLeft then Self.DoMouseSelectStart(Item, Shift); Self.DoMouseSelectFinish(Item, Shift); end; procedure TForm1.FormCreate(Sender: TObject); var i: Integer; begin LB := TListBox.Create(Self); LB.Parent := Self; { works for other MultiSelectStyles too } LB.MultiSelectStyle := TMultiSelectStyle.None; with LB.Items do begin for i in [0..3] do Add('Item ' + IntToStr(i)); end; { we need to know the class type of the SelectionController } SC := TListBoxAccess(LB).SelectionController; PatchMouseSelectFinish; // of the actual SC { Needed to see whether ListBox selection 'works' as expected, when you click on items with the right mouse button. } Application.OnIdle := DoOnIdle; { Optional, for more info ... } // LB.Align := TAlignLayout.Client; // InspectVMT(''); end; procedure TForm1.PatchMouseSelectFinish; var p: Pointer; n: UINT_PTR; vi: Integer; begin // vi := 7; { known value in 10.3.3 } vi := GetVirtualMethodIndex; if vi > 0 then begin { see https://en.delphipraxis.net/topic/1922-patch-a-private-virtual-method/ } {$POINTERMATH ON} p := @FixedMouseSelectFinish; WriteProcessMemory( GetCurrentProcess, @PPointer(SC.ClassType)[vi], @p, SizeOf(Pointer), n); end; end; function TForm1.GetVirtualMethodIndex: Integer; var LContext: TRttiContext; LType: TRttiType; LMethods: TArray<TRttiMethod>; l: Integer; m: TRttiMethod; begin { get the index of the public virtual method in VMT, of the class that is actually used, a descendent of TListBoxSelector } result := -1; LContext := TRttiContext.Create; try LType := LContext.GetType(SC.ClassType); LMethods := LType.GetMethods('MouseSelectFinish'); l := Length(LMethods); if l > 0 then begin { we want the first one } m := LMethods[0]; result := m.VirtualIndex; end; finally LContext.Free; end; end; procedure TForm1.InspectVMT(const AMethodName: string); var LContext: TRttiContext; LType: TRttiType; LMethods: TArray<TRttiMethod>; i: Integer; rm: TRttiMethod; mn: string; cn: string; vi: Integer; begin LB.Items.Clear; LContext := TRttiContext.Create; try LType := LContext.GetType(SC.ClassType); if AMethodName = '' then LMethods := LType.GetMethods else LMethods := LType.GetMethods(AMethodName); for i := 0 to Length(LMethods) - 1 do begin rm := LMethods[i]; cn := rm.Parent.Name; mn := rm.ToString; vi := rm.VirtualIndex; LB.Items.Add(Format('%3d %p %s.%s', [vi, rm.CodeAddress, cn, mn])); end; finally LContext.Free; end; end; procedure TForm1.DoOnIdle(Sender: TObject; var Done: Boolean); begin Caption := IntToStr(LB.ItemIndex); Done := True; end; end. I am patching a public virtual method that appears in TListBoxSelector, which is NOT overridden in TSingleSelectionController. VMT, from the styled test poject (not minimal): Notes: The root problem is with concrete classes declared in implementation section. a) I cannot typecast to these types. MethodPtr := TSingleSelectionController(@VMT).MouseSelectFinish; // nope MethodPtr := TRggSelectionController(@VMT).MouseSelectFinish; // ok b) In ( for LType in LContext.GetTypes do ) I cannot find a type by name, by checking for (LType.Name = 'TSingleSelectionController') // nope by checking for (LType.Name = 'TRggSelectionController') // ok. c) But I can do LType := LContext.GetType(SC.ClassType); // SC = TSingleSelectionController So, I could make use of VirtualIndex because I got Access to the type first, via TListBoxAccess. - You can test out my fix if you want.

The Opacity parameter should be between 0 and 1. RectF is not the problem, even if specified too large. A stretched version of the original (aBMP) is drawn on top of aBMP, as expected. I can see it in an Image component, and in the file on disk. TempBMP, a copy of aBMP is needed it seems, ok. I noticed that the copy of aBMP needs to be made outside of the BeginScene/EndScene block, ok? Can you reproduce a problem without saving to disk? What exactly is the problem - how do you show the image? { rectangle setup } SrcFull := RectF(0, 0, tempBMP.Width, tempBMP.Height); DstLeft := RectF(0, 0, aBMP.Width / 3, aBMP.Height); aBMP.Canvas.DrawBitmap(tempBMP, SrcFull, DstLeft, 1.0, True);

Assign to tempBMP outside of BeginScene / EndScene? procedure TForm1.InsertOnMyLeft(aBMP: TBitmap); var tempBMP: TBitmap; RecFull: TRectF; RecLeft: TRectF; begin tempBMP := TBitmap.Create; try tempBMP.Assign(aBMP); // <-- aBMP.Canvas.BeginScene; RecFull := RectF(0, 0, aBMP.Width-1, aBMP.Height-1); RecLeft := RectF(0, 0, Round((aBMP.Width-1) / 2), Round((aBMP.Height-1) / 1)); aBMP.Canvas.DrawBitmap(tempBMP, RecFull, RecLeft, 0.5, True); aBMP.Canvas.EndScene; finally tempBMP.Free; end; end;

I am adding an explanation for the solution and then a question. Explanation The selection of Items in a ListBox is supposed to be done with the left mouse button down or with a single finger on a touchscreen. There is a bug - when you use the right mouse button on the desktop. It will set ItemIndex but will not update the selection. It turns out that it is difficult to prevent this. And this difficulty led me to the solution. Rather than to prevent the use of the right and middle mouse buttons to change ItemIndex - I will try to do it properly. To do it properly means that the selection should be updated. Wild guess: "It is difficult to finish what you have not started." So you better start the thing before you finish it? See code - it works. imlementation type TSingleSelectionController = class(TListBoxSelector) public { to be explained: } procedure MouseSelectFinish(const Item: TListBoxItem; const Button: TMouseButton; const Shift: TShiftState); override; end; procedure TSingleSelectionController.MouseSelectFinish(const Item: TListBoxItem; const Button: TMouseButton; const Shift: TShiftState); begin { Only one new line;-) } if Button <> TMouseButton.mbLeft then DoMouseSelectStart(Item, Shift); DoMouseSelectFinish(Item, Shift); end; end. Question What hack can I apply to a) replace one public virtual method in TListBoxSelection? or b) override one public virtual method in TSingleSelectionController? So far I made the change in a copy of the unit - a) FMX.ListBox for TListBoxSelection or b) FMX.ListBox.Selection for TSingleSelectionController ( The problem is of course that TListBoxSelection is public but abstract, and concrete classes are declared in the implementation section. ) A patched version of TSingleSelectionController will be used in the minimal test project below. implementation {$R *.fmx} procedure TForm1.FormCreate(Sender: TObject); var i: Integer; begin { TMultiSelectionStyle.None --> TSingleSelectionController } { TMultiSelectionStyle.Default --> TMultiSelectionController } { TMultiSelectionStyle.Extended --> TExtendedSelectionController } ListBox1.MultiSelectStyle := TMultiSelectStyle.None; with ListBox1.Items do begin for i in [0..3] do Add('Item ' + IntToStr(i)); end; Application.OnIdle := DoOnIdle; end; procedure TForm1.DoOnIdle(Sender: TObject; var Done: Boolean); begin Caption := IntToStr(ListBox1.ItemIndex); Done := True; end; end. The hack I am asking for should not copy whole units!

No need to report the right mouse button bug, it exists already. RSP-28235 But I think I have the solution: procedure TListBoxSelector.MouseSelectFinish(const Item: TListBoxItem; const Button: TMouseButton; const Shift: TShiftState); begin if Button <> TMouseButton.mbLeft then begin DoMouseSelectStart(Item, Shift); end; DoMouseSelectFinish(Item, Shift); end;

Best practice recommendations: For simple case of ListBox with 4 Items, only one of which should be selectable, do this: a) use OnItemClick, not OnClick b) use TMultiSelectStyle.Default, not TMultiSelectStyle.None (the default) c) do not use the right mouse button to select items d) use TListView if you can My new minimal example - which monitors ItemIndex - shows that the right mouse button can change ItemIndex, so that it becomes out of sync with the selection. unit FrmMain; interface uses System.SysUtils, System.Classes, FMX.Controls.Presentation, FMX.Forms, FMX.Graphics, FMX.ListBox, FMX.StdCtrls, FMX.Objects, FMX.Layouts, FMX.Types, FMX.Controls; type TForm1 = class(TForm) ListBox1: TListBox; Text1: TText; NoneBtn: TSpeedButton; DefaultBtn: TSpeedButton; ExtendedBtn: TSpeedButton; procedure FormCreate(Sender: TObject); procedure ListBox1ItemClick(const Sender: TCustomListBox; const Item: TListBoxItem); procedure NoneBtnClick(Sender: TObject); procedure DefaultBtnClick(Sender: TObject); procedure ExtendedBtnClick(Sender: TObject); private procedure DoOnIdle(Sender: TObject; var Done: Boolean); end; var Form1: TForm1; implementation {$R *.fmx} procedure TForm1.NoneBtnClick(Sender: TObject); begin ListBox1.MultiSelectStyle := TMultiSelectStyle.None; end; procedure TForm1.DefaultBtnClick(Sender: TObject); begin ListBox1.MultiSelectStyle := TMultiSelectStyle.Default; end; procedure TForm1.ExtendedBtnClick(Sender: TObject); begin ListBox1.MultiSelectStyle := TMultiSelectStyle.Extended; end; procedure TForm1.FormCreate(Sender: TObject); var gn: string; ML: TStrings; begin ReportMemoryLeaksOnShutdown := True; ML := ListBox1.Items; ML.Add('Item 0'); ML.Add('Item 1'); ML.Add('Item 2'); ML.Add('Item 3'); ListBox1.MultiSelectStyle := TMultiSelectStyle.Default; ListBox1.OnItemClick := ListBox1ItemClick; NoneBtn.StaysPressed := True; DefaultBtn.StaysPressed := True; ExtendedBtn.StaysPressed := True; NoneBtn.IsPressed := ListBox1.MultiSelectStyle = TMultiSelectStyle.None; DefaultBtn.IsPressed := ListBox1.MultiSelectStyle = TMultiSelectStyle.Default; ExtendedBtn.IsPressed := ListBox1.MultiSelectStyle = TMultiSelectStyle.Extended; gn := 'MultiSelectEnum'; NoneBtn.GroupName := gn; DefaultBtn.GroupName := gn; ExtendedBtn.GroupName := gn; Application.OnIdle := DoOnIdle; end; procedure TForm1.ListBox1ItemClick(const Sender: TCustomListBox; const Item: TListBoxItem); begin Caption := IntToStr(Item.Index); end; procedure TForm1.DoOnIdle(Sender: TObject; var Done: Boolean); begin Text1.Text := IntToStr(ListBox1.ItemIndex); Done := True; end; end. ( Using a class helper for TListBoxSelector.MouseSelectFinish is not possible. )

ClearSelection; Now only one item will be shown as selected at any time, But FCurrent alias ItemIndex can still be changed with right mouse button click on another item, without beeing reflected by the visual selection. Which should be dealt with in MouseSelectFinish? procedure TRggSelectionController.MouseSelectFinish(const Item: TListBoxItem; const Button: TMouseButton; const Shift: TShiftState); begin { added test for button } if Button <> TMouseButton.mbLeft then Exit; inherited; end;

Since I have 'played' with TSingleSelectionController a bit, I want to disclose a Feature! With TMultiSelectStye.None (the default for TListBox), it is still possible to select more then one Item, albeit with the illegal help of the right mouse button. This is because the right mouse button will set FCurrent, wich will then derail the proper deselection of the previously selected item - when you left click on another item, which is not the selected and not the current. In other words, the Selected Item and the Current Item may get out of sync when the user is trying something wierd with left and right mouse buttons. Note: On the touch screen, a long tap maps to right mouse button. { Playing with 4 Items: 1) Click Item 1 with left mouse button. Item 1 becomes selected FCurrent := 1 2) Click Item 3 with right mouse button Item 1 still selected Item 3 not selected FCurrent := 3 3) Click Item 2 with left mouse button FCurrent = 3 (still, when DoMouseSelectStart is called) Item 3 will be deselected (but it was not selected, no change) Item 2 becomes selected as well Item 1 still selected FCurrent := 2 ( after click) } procedure TSingleSelectionController.DoMouseSelectStart(const Item: TListBoxItem; const Shift: TShiftState); begin if (FUserSetIndex = -1) and (Item.Index <> FCurrent) then begin { will deselect current } SetSelected(GetCurrentItem, False); // <-- depends on FCurrent being 'correct' if SetCurrent(Item.Index) then Item.SetIsSelectedInternal(True, False); end; end;

OK, OnItemClick is much better, got it - only now. Perhaps OnClick should be deprecated? https://stackoverflow.com/questions/48813666/firemonkey-tlistbox-onclick-which-item-is-clicked https://stackoverflow.com/questions/19822639/translating-onclick-to-ontouch-or-something-similiar

I can register my own TListBoxSelector derived class and then create a TListBox at runtime, which uses the custom TListBoxSelector, but the classes to inherit from are all private, defined in implementation section of FMX.ListBox.Selection. I did it anyway, just to test out if it works. procedure TRggSelectionController.MouseSelectStart(const Item: TListBoxItem; const Button: TMouseButton; const Shift: TShiftState); begin if Button <> TMouseButton.mbLeft then Exit; // if (FListBox.AniCalculations.TouchTracking <> []) and (Item.Index <> FCurrent) then // DelayedMouseDown(Item, Shift) // else DoMouseSelectStart(Item, Shift); end; { in FormCreate: } TListBoxSelectorFactory.RegisterSelector(TMultiSelectStyle.None, TRggSelectionController); ListBox.Free; ListBox := TListBox.Create(Self); ListBox.Parent := Self; ListBox.Position.Y := 100; ListBox.Position.Y := 200; ListBox.OnClick := ListBoxClick; I am using the Listbox in a desktop application, and when I am navigating the items with the arrow keys, I do not want to do anything immediately. Only when the user clicks, or presses the space character, should an action be triggered. That is why I tried with OnClick instead of OnChange. OnChange is working, but it is called before OnClick, so I cannot just set a flag in OnClick, to be evaluated in OnChange, that does not work. Best workaround still to be determined.

Just found out that it is an already Open issue: RSP-19266 You can create a test environment for the issue on the desktop which should be good enough to investigate, by changing one line in the implementation section, in a copy of unit FMX.ListBox. procedure TListBoxSelector.MouseSelectStart(const Item: TListBoxItem; const Button: TMouseButton; const Shift: TShiftState); begin if Button <> TMouseButton.mbLeft then Exit; // if (FListBox.AniCalculations.TouchTracking <> []) and (Item.Index <> FCurrent) then if (Item.Index <> FCurrent) then DelayedMouseDown(Item, Shift) else DoMouseSelectStart(Item, Shift); end;

I used PAServer and 64 Bit remote debugging - for the first time - to find out more, with two breakpoints: 1) One breakpoint in OnClick handler. 2) Another breakpoint in TListBoxSelector.SetCurrent. I got different call stacks between Desktop and Tablet. On the tablet computer the OnClick handler is called before the first call to SetCurrent. And this is the very problem! It is of course important that TListBoxSelector.FCurrent be set to the correct value before my OnClick handler is called. /// <summary>Timer used for DelayedMouseDown</summary> FSelectionTimer: TTimer; function TListBoxSelector.SetCurrent(const Index: Integer): Boolean; begin Result := FCurrent <> Index; FCurrent := Index; // <-- ItemIndex end; procedure TListBoxSelector.MouseSelectStart(const Item: TListBoxItem; const Button: TMouseButton; const Shift: TShiftState); begin if Button <> TMouseButton.mbLeft then Exit; if (FListBox.AniCalculations.TouchTracking <> []) and (Item.Index <> FCurrent) then DelayedMouseDown(Item, Shift) // <-- Surface tablet else DoMouseSelectStart(Item, Shift); // <-- Desktop end; procedure TListBoxSelector.DelayedMouseDown(const ItemDown: TListBoxItem; const Shift: TShiftState); begin if FSelectionTimer = nil then FSelectionTimer := TSelectionTimer.CreateTimer(Self); TSelectionTimer(FSelectionTimer).Reload(ItemDown, Shift); end; Now I am confident that some of you will be able to reproduce.

Update - the problem is reproducible on my Surface tablet with scaling 2.0, but not - as I have just learned - on my Retina iMac with the same scaling, in the bootcamp partition. Surprise.

No solution so far, just the test project which will show the issue. Whether OnClick 'works' depends on where you test. On my Surface tablet it it does not work. ItemIndex will be the previously clicked item, not the item you just clicked on. And the first time you click, the handler will not be called at all. Latest: I verified that OnChange works as expected, and I looked up the specific model info of the problem device: procedure TFormMain.ListBoxChange(Sender: TObject); begin { works as expected } // HandleClick(Listbox.ItemIndex); end; procedure TFormMain.ListBoxClick(Sender: TObject); begin { does not work on Surface Pro (5. Gen), Modell 1796 m3 } HandleClick(Listbox.ItemIndex); end; procedure TFormMain.HandleClick(ii: Integer); begin if ii > -1 then begin Inc(Counter); Caption := ListBox.Items[ii] + ' - ' + IntToStr(Counter); end; end;

unit FrmMain; interface uses System.SysUtils, System.Types, System.UITypes, System.Classes, FMX.Types, FMX.Controls, FMX.Forms, FMX.Graphics, FMX.Layouts, FMX.ListBox, FMX.ListView.Types, FMX.ListView.Appearances, FMX.ListView.Adapters.Base, FMX.ListView; type TFormMain = class(TForm) ListBox: TListBox; ListView: TListView; procedure FormCreate(Sender: TObject); procedure ListBoxClick(Sender: TObject); procedure ListBoxKeyUp(Sender: TObject; var Key: Word; var KeyChar: Char; Shift: TShiftState); procedure ListViewItemClick(const Sender: TObject; const AItem: TListViewItem); procedure FormDestroy(Sender: TObject); private Counter: Integer; ML: TStrings; end; var FormMain: TFormMain; implementation {$R *.fmx} procedure TFormMain.FormCreate(Sender: TObject); var i: Integer; li: TListViewItem; begin ReportMemoryLeaksOnShutdown := True; ML := TStringList.Create; ML.Add('Item 0'); ML.Add('Item 1'); ML.Add('Item 2'); ML.Add('Item 3'); Listbox.Items := ML; ListView.ItemAppearanceName := 'ListItem'; ListView.ItemAppearance.ItemHeight := 24; ListView.ItemAppearanceObjects.ItemObjects.Accessory.Visible := False; ListView.ItemAppearanceObjects.ItemObjects.Text.Font.Family := 'Consolas'; ListView.ItemAppearanceObjects.ItemObjects.Text.Font.Size := 16; ListView.ItemAppearanceObjects.ItemObjects.Text.TextColor := TAlphaColors.Dodgerblue; ListView.ItemAppearanceObjects.HeaderObjects.Text.Visible := False; ListView.ItemAppearanceObjects.FooterObjects.Text.Visible := False; ListView.OnItemClick := ListViewItemClick; for i := 0 to ML.Count-1 do begin li := ListView.Items.Add; li.Text := ML[i]; end; end; procedure TFormMain.FormDestroy(Sender: TObject); begin ML.Free; end; procedure TFormMain.ListViewItemClick(const Sender: TObject; const AItem: TListViewItem); var ii: Integer; begin ii := AItem.Index; if ii > -1 then begin Inc(Counter); Caption := ML[ii] + ' - ' + IntToStr(Counter); end; end; procedure TFormMain.ListBoxClick(Sender: TObject); var ii: Integer; begin if ListBox.Selected = nil then begin Inc(Counter); Exit; end; ii := ListBox.ItemIndex; if ii > -1 then begin Inc(Counter); Caption := ML[ii] + ' - ' + IntToStr(Counter); end; end; procedure TFormMain.ListBoxKeyUp(Sender: TObject; var Key: Word; var KeyChar: Char; Shift: TShiftState); begin if KeyChar = ' ' then ListBoxClick(nil); end; end.

Works for me! Except for two minor observations: a) in Winapi.D2DMissing there are references to some enum values (const) which are not available in my Rio installation, but those can be looked up on the Internet. const D2D1_INTERPOLATION_MODE_NEAREST_NEIGHBOR = 0; //D2D1_INTERPOLATION_MODE_DEFINITION_NEAREST_NEIGHBOR; ... b) GrayScale can be set only once, thereafter it fails with EOSError, Code 87, Wrong Parameter?

In FMX: Is TComboBox.Text is a missing property? This post is about the best possible way to handle a little problem, with as little change to existing code as possible, just after porting old code from VCL to FMX. Test code to play with: var Counter: Integer = 0; procedure TForm1.ComboBox1Change(Sender: TObject); var s: string; begin // s := ComboBox1.Text; // does not compile { ComboBox1.Selected.Text is what you want, but Selected can be nil! } if Combobox1.Selected = nil then begin Counter := Counter + 1; Caption := IntToStr(Counter); Exit; end; s := ComboBox1.Selected.Text; { Old code uses string comparision to decide what to do. } { ... } // Caption := s; end; procedure TForm1.Button1Click(Sender: TObject); begin ComboBox1.Items.Text := 'Hello World'; ComboBox1.ItemIndex := 0; end; procedure TForm1.Button2Click(Sender: TObject); var SL: TStrings; begin SL := TStringList.Create; SL.Add('Foo'); SL.Add('Bar'); SL.Add('Vote for RSP-29811'); ComboBox1.Items := SL; ComboBox1.ItemIndex := 2; SL.Free; end; Consider an existing application that you port from VCL. Not only will you have to change code to make it compile, you will also have to write extra code to keep it from crashing.

It can be confusing, so I double-checked: ComboBox.Clear does not trigger OnChange ComboBox.Items.Clear will trigger OnChange (with Selected = nil) It is after calling ComboBox.Clear that you can observe the first-attempt-anomaly. Assigning to Items will involve Items.Clear, and the Selected = nil problem, which the feature request is aiming to deal with in a better way. The fact that OnChange is not called after Combo.Clear may be a problem for the logic of your program. But that does not invalidate the feature request. The attached form contains the updated test code. FrmMain.zip

The Problem (ComboBox.Selected = nil in OnChange) does not happen the first time you swap the content of Items. It is happening from the second time onwards. Can be shown easily with another test button that calls ComboBox1.Clear. This will reset the test cycle. TComboBoxHelper works as expected and is 3rd best option for me. Second best option in my ranking is to inherit from TComboBox, preferred because I do create all components at runtime. Best option so far and by far is of course to add the property directly. No one came out with the idea for 8 years or so. And then it took me two days (too long) after running into the problem, before I refactored and used my own combobox - a little success story. So this is why I made an exception to the rule and went on record with a feature request for something otherwise very simple. We are now up to two votes. A big number for me, a small step for Delphi. Thanks to Emba for opening the 'new feature' request. Let's see how it goes. 👈

I found out why and I post the test code without talking too much: unit FrmMain; interface uses System.SysUtils, System.Classes, System.UITypes, System.Rtti, FMX.Types, FMX.Forms, FMX.StdCtrls, FMX.Objects, FMX.Controls, FMX.Controls.Presentation; type TMyPanel = class(TPanel) public function FindStyleResource(const AStyleLookup: string; const AClone: Boolean = False): TFmxObject; override; end; TFormMain = class(TForm) procedure FormCreate(Sender: TObject); private Button: TButton; Panel: TPanel; procedure Button1Click(Sender: TObject); end; var FormMain: TFormMain; implementation {$R *.fmx} procedure TFormMain.FormCreate(Sender: TObject); begin Panel := TMyPanel.Create(Self); Panel.Parent := Self; Panel.Position.X := 100; Panel.Position.Y := 100; Button := TButton.Create(Self); Button.Parent := Self; Button.Text := 'Test'; Button.OnClick := Button1Click; end; procedure TFormMain.Button1Click(Sender: TObject); begin Panel.StylesData['Something.Fill.Color']:= TAlphaColors.Dodgerblue; // Panel.StylesData['.Fill.Color']:= TAlphaColors.Dodgerblue; end; { TMyPanel } function TMyPanel.FindStyleResource(const AStyleLookup: string; const AClone: Boolean): TFmxObject; function FindOnTopLevel(const Name: string): TFmxObject; var Child: TFmxObject; begin for Child in Children do begin if SameText(Child.StyleName, Name) then begin Exit(Child); end; end; Result := nil; end; begin result := nil; { New: try something even if ResourceLink has no children ! } if ResourceLink.ChildrenCount = 0 then begin result := FindOnTopLevel(''); if result is TRectangle then Exit; end; inherited; end; (* There is a problem when FindStyleResource is called on a FResourceLink instance which has no children. function TFmxObject.FindStyleResource(const AStyleLookup: string; const Clone: Boolean = False): TFmxObject; begin if (AStyleLookup <> '') and (FChildren <> nil) and (FChildren.Count > 0) then begin // not executed because TPanel.ResourceLink has no children end; end; FMX.Types.TFmxObject.FindStyleResource('',False) FMX.Controls.TStyledControl.FindStyleResource(???,???) FMX.Controls.Presentation.TPresentedControl.FindStyleResource('',False) FMX.Controls.TStyledControl.StyleDataChanged(???) FMX.Controls.Presentation.TPresentedControl.StyleDataChanged('.Fill.Color') FMX.Controls.TStyledControl.SetStyleData('.Fill.Color') FrmMain.TFormMain.Button1Click($3F30880) *) end.

I see the same OsHardwareAbstractionlayer = 10.0.18362.752 But my Operating System Build Number shown in Settings/System/Info is 18363.778

If global variable myQuery was a field of a class then it would be automatically initialized to nil. And if the procedure createMyQuery was a method of that class you would not need to pass the myQuery instance around as a parameter. Classes can be used with console application as well, just saying.

MyQuery should be initialized to nil. //procedure createMyQuery(query: TFDQuery; const Sql: String=''); procedure createMyQuery(var query: TFDQuery; const Sql: String=''); begin if query = nil then query := TFDQuery.Create(nil); query.Connection := myDatabase; query.SQL.Text := Sql; end; var myQuery: TFDQuery; begin myQuery := nil; createMyQuery(myQuery,'select * from table'); end;

FMX feature: If you inherit from TPanel twice it becomes transparent, like TLayout. Context: I have a base class which inherits from TPanel. And then I actually use a class that inherits from that base class. I think I will use a TLayout, but do you have an explanation why my Panel is loosing style? unit Unit1; interface uses System.SysUtils, System.Types, System.UITypes, System.Classes, FMX.Types, FMX.Controls, FMX.Forms, FMX.Graphics, FMX.Controls.Presentation, FMX.StdCtrls, FMX.Layouts; type // TSpeedPanelClass = TToolbar; // TSpeedPanelClass = TLayout; TSpeedPanelClass = TPanel; TSpeedPanelBase = class(TSpeedPanelClass); TSpeedPanel = class(TSpeedPanelBase); TForm1 = class(TForm) Button1: TButton; Button2: TButton; procedure FormCreate(Sender: TObject); procedure Button1Click(Sender: TObject); procedure Button2Click(Sender: TObject); private Counter: Integer; Y: Integer; procedure InitSpeedPanel(sp: TSpeedPanelClass); procedure SpeedButtonClick(Sender: TObject); end; var Form1: TForm1; implementation {$R *.fmx} procedure TForm1.FormCreate(Sender: TObject); begin Button1.Position.X := 24.0; Button1.Position.Y := 8.0; Button2.Position.X := 112.0; Button2.Position.Y := 8.0; Fill.Color := TAlphaColors.Cornflowerblue; Fill.Kind := TBrushKind.Solid; Y := 50; end; procedure TForm1.Button1Click(Sender: TObject); var sp: TSpeedPanelClass; begin sp := TSpeedPanelBase.Create(Self); InitSpeedPanel(sp); end; procedure TForm1.Button2Click(Sender: TObject); var sp: TSpeedPanelClass; begin sp := TSpeedPanel.Create(Self); InitSpeedPanel(sp); end; procedure TForm1.InitSpeedPanel(sp: TSpeedPanelClass); var sb: TSpeedButton; begin Inc(Counter); sp.Parent := Self; sp.Position.X := 0; sp.Position.Y := Y; sp.Height := 40; sp.Width := 200; sb := TSpeedButton.Create(sp); sb.Parent := sp; sb.Text := 'SpeedButton' + IntToStr(Counter); sb.Tag := Counter; sb.OnClick := SpeedButtonClick; Y := Y + 50; end; procedure TForm1.SpeedButtonClick(Sender: TObject); begin Caption := Format('Btn %d clicked.', [(Sender as TComponent).Tag]); end; end.