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Anders Melander
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Everything posted by Anders Melander
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VCL UI Design Challenge for Delphi Developers π‘
Anders Melander replied to bravesofts's topic in VCL
Why? In a browser? -
Multithread and thread-safe TClientDataSet?
Anders Melander replied to snodev's topic in RTL and Delphi Object Pascal
Yes. I think you should drop the idea of the workers writing to a dataset. Write to a lock free queue instead and then read from the queue from a separate thread. -
Multithread and thread-safe TClientDataSet?
Anders Melander replied to snodev's topic in RTL and Delphi Object Pascal
If by "clone" you mean a cursor clone, then the master and the clone shares the same data and modification from one thread will alter data seen by other threads (with no automatic synchronization AFAIR). So: Not thread safe. If by "clone" you mean a distinct private copy of the data, then yes it's safe. Apart from that, do you have a specific reason to use TClientDataSet instead of TFDMemTable? TFDMemTable also has clonable cursors (with pretty much the same restrictions as TClientDataSet I would think). With TFDMemTable you at least have the source and can see for yourself what goes on. -
Yeah well, threads do come with their own challenges and I have a feeling that the OP "just want it work" and get on with business. I agree that blocking the main thread for 5 seconds is too long - and I'm pretty sure Windows isn't too happy about it either.
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I can't believe I just made a case for Application.ProcessMessages after 25 years of trying to get people to stop using it π€¦ββοΈ
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The purpose of Application.ProcessMessages would be to have any pending messages in the queue processed. If there is a mouse-click message in the queue then it will be processed but will do nothing because the control being clicked is disabled. Without Application.ProcessMessages then the mouse-click message will still be in the queue after the control has been enabled and will therefore be handled as a click when the queue is pumped.
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I can't see why. Please explain.
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I agree wrt avoiding Application.ProcessMessages but... If the form is modal then you can disable the form instead of the panel and then it should be (relatively) safe to use Application.ProcessMessages. Place it right before you enable the form again.
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Exactly
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Yes it will. The reason it will not pump messages is that it's not being given an opportunity to do so. This is the equivalent: Button.Enabled := False; Sleep(1000); Button.Enabled := True;
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That doesn't solve the problem. Read the prior replies. Why test for csAcceptsControls? ο»ΏIt's a design-time option.
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...not because the panel is disabled but because the stuff in between doesn't process messages - in case you wondered.
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It's because you aren't processing any windows messages while the panel is disabled, so when you enable it again the mouse click message is still waiting in the message queue.
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https://meta.wikimedia.org/wiki/Cunningham's_Law
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https://docwiki.embarcadero.com/Libraries/Athens/en/Data.DB.TDataSource TDataSource is the wrong layer for something like caching. You need to sit between TDataSource and TDataSet. What happens if you have two datasources connected to a single dataset and one of them modifies the data? Now you have two different views of what the data looks like... What is the point of spawning a thread to update the cache if all the thread does is call Synchronize to update the cache from the main thread? I know ElevateDB has had resistance against FireDAC in the past but if they have gotten wiser, and support FireDAC now, then you could have used one of the FireDAC datasets. They all support caching and briefcase mode. TClientDataSet could also have been used.
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23929_tdocktabset_sample_application.ZIP Last time I looked, and it's been a while, the docking manager used in the IDE was a different one from the one in the VCL. The behavior of the VCL docking manager is (was?) hardcoded into TControl in a way that made it impossible to fix from the outside. I would say it depends on the users. I was talking about typical non-technical end-users. Obviously highly technical users, such as developers, have no problems using docking.
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I gave up on the VCLs docking a long time ago, after having spent a ridiculous amount of time trying to work around its numerous bugs. It's broken beyond repair and should be deprecated and replaced. I use DevExpress docking now and I think it works really well. That said, from watching our users, and even our in-house supporters, I can tell you that ordinary users don't understand how to use docking at all. It's really painful to watch them trying to get the dock layout they want. So I think it's best to try and limit the range of docking features available to the user. For example: No auto-hide panels, no docked maximize/minimize. Even floating dock panels might be too advanced or simply not usable (undocked forms obscure the windows below) or unnecessary (multi-monitors are being replaced by wide monitors).
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Does anyone know a delphi component that can play videos from a stream
Anders Melander replied to ToddFrankson's topic in VCL
Another option is to use DirectShow. I know that can also be made to load from a stream. Google "Delphi DirectShow" -
Does anyone know a delphi component that can play videos from a stream
Anders Melander replied to ToddFrankson's topic in VCL
The application is closed source but I have attached the relevant unit (and one dependency). There are a lot of unrelated dependencies in that unit, since it is a part of a large resource editor framework, so unfortunately it's not as readable as it could be. The unit implements a viewer for video and sound media resources. amResourceViewMedia.pas amResourceViewMedia.dfm VFW.pas -
Does anyone know a delphi component that can play videos from a stream
Anders Melander replied to ToddFrankson's topic in VCL
I have some code that I use in my resource editor to display video from a memory stream, so it's definitely possible. I just looked and it's about 500-600 lines of code and involves a custom I/O handler among other horrors. Here's a screenshot: And here's a video: Hmm. Never mind with the video. I can't figure out how to create a video this forum supports. -
One thing you can do, to direct activity to the discussions, is to convert issues to discussion unless they actually pertain to an acknowledged bug or an accepted change/feature/enhancement. That way the issue list becomes a list of work items and the discussions everything else.
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How to work with published properties of the Variant type correctly.
Anders Melander replied to dmitrybv's topic in Delphi IDE and APIs
Yes; It's called a tarpit π -
Does anyone know a delphi component that can play videos from a stream
Anders Melander replied to ToddFrankson's topic in VCL
There's the old TMediaPlayer but AFAIR it's a pain (but possible) to get to work with TStream. A better alternative would be to import the type library for the Windows Media Player ActiveX and use that. https://chapmanworld.com/windows-media-player-in-delphi/ -
How to work with published properties of the Variant type correctly.
Anders Melander replied to dmitrybv's topic in Delphi IDE and APIs
Apparently the standard design-time property editors doesn't fully support Variant. https://stackoverflow.com/questions/29979950/how-to-correctly-set-a-variant-published-property I've looked at the code of the property editor but I can't make sense of it so I can't tell if it should work or not. I would have to debug Delphi in Delphi to figure it out and... Nope. Don't compare against a boolean value. Use boolean logic: if not VarSameValue(FCheckedValue, Value)then Same with the test in IsCheckedValueStored. Just set result directly: Result := not VarSameValue(FCheckedValue, True); -
How do I close a modal form without ModalResult being set to mrCancel ?
Anders Melander replied to dormky's topic in VCL
Huh? var Msg: TMsg; while (PeekMessage(Msg, 0, WM_SETCURSOR, WM_SETCURSOR, PM_REMOVE)) do begin if (Msg.message = WM_QUIT) then begin PostQuitMessage(Msg.wParam); exit; end; DispatchMessage(Msg); end;