Castle Game EngineIntroduction Units Class Hierarchy Classes, Interfaces, Objects and Records Types Variables Constants Functions and Procedures Identifiers |
Class TGLApplication
Unit
CastleWindow
Declaration
type TGLApplication = class(TComponent)
Description
Application, managing all open TCastleWindowBase (OpenGL windows). This tracks all open instances of TCastleWindowBase and implements message loop. It also handles some global tasks like managing the screen (changing current screen resolution and/or bit depth etc.)
The only instance of this class should be in Application variable. Don't create any other instances of class TGLApplication , there's no point in doing that.
Hierarchy
- TComponent
- TGLApplication
Overview
Fields
Methods
Properties
Description
Fields
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VideoResizeWidth: integer; |
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VideoResizeheight: integer; |
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Methods
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function VideoSettingsDescribe: string; |
Describe the changes recorded in variables VideoXxx, used by VideoChange and TryVideoChange. This is a multiline string, each line is indented by 2 spaces, always ends with CastleUtils.NL.
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procedure VideoChange(OnErrorWarnUserAndContinue: boolean); |
Change the screen size, color bits and such, following the directions you set in VideoColorBits, VideoResize, VideoResizeWidth / VideoResizeHeight, and VideoFrequency variables. This actually just calls TryVideoChange and checks the result.
If not success: if OnErrorWarnUserAndContinue then we'll display a warning and continue. If not OnErrorWarnUserAndContinue then we'll raise an Exception.
Exceptions raised
Exception
- If video mode change failed, and OnErrorWarnUserAndContinue = false.
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procedure VideoReset; |
Return default screen video mode. If you never called TryVideoChange (with success), then this does nothing. This is automatically called in Application.Destroy, so at finalization of this unit. This way your game nicely restores screen resolution for user.
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function ScreenHeight: integer; |
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function ScreenWidth: integer; |
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function OpenWindowsCount: integer; |
List of all open windows.
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function ProcessMessage(WaitForMessage, WaitToLimitFPS: boolean): boolean; |
Process messages from the window system. You have to call this repeatedly to process key presses, mouse events, redraws and everything else. Messages are processed and appropriate window callbacks are called, like TCastleWindowBase.OnDraw, TCastleWindowBase.OnIdle, TCastleWindowBase.OnKeyPress and many others.
For simple programs calling the Run method is usually the best solution, Run just calls ProcessMessage in a loop. Manually using the ProcessMessage method allows you to implement modal dialog boxes (generally any kind of "display something until something happens" behavior). Make your own event loop like this:
while not SomethingHappened do
Application.ProcessMessages(...);
Often this is used together with TGLMode, TGLModeFrozenScreen and similar utilities from CastleWindowModes unit. They allow you to temporarily replace window callbacks with new ones, and later restore the original ones. This is useful for behavior similar to modal dialog boxes.
Returns True if we should continue, that is if Quit method was not called (directly or by closing the last window). If you want to check it (if you allow the user at all to close the application during modal box or such) you can do:
while not SomethingHappened do
if not Application.ProcessMessage(...) then
Break;
Do not assume too much about message processing internals. For example, not all ProcessMessage calls cause redraw, even if redraw is requested by PostRedisplay. When we have messages to process, we generally don't call redraw or even OnIdle.
Parameters
- WaitForMessage
- If
True (and some other conditions are met, for example we do not have to call OnIdle continuosly) then we can block, waiting for an event to process.
Set this to True whenever you can, that is whenever your program only responds to user inputs (as opposed to making some operations, like animation or loading or ray-tracing something). Generally, when SomethingHappened from the example pseudo-code above can only be changed by user events (e.g. user has to click something; nothing happens if user doesn't click for 5 minutes or 5 hours). This allows to let OS and CPU have some rest, and spend time on other applications, or just sleep and conserve laptop battery power.
- WaitToLimitFPS
- If
True , then we have backup mechanism for limiting CPU usage. When WaitForMessage mechanism cannot be used (becasue WaitForMessage is False or some other conditions disallow it), and user doesn't throw events at us (we don't want to sleep when user produces many events e.g. by mouse move), then we can do a small sleep to stabilize number of ProcessMessage calls at LimitFPS per second.
Set this to True whenever you can, that is whenever you don't need ProcessMessage to return as fast as it can. For example, when you're displaying some animation, then displaying LimitFPS frames should be enough. OTOH, if you really do something that should be done as fast as possible (like loading some file or ray-tracing) you probably have to set this to False .
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function ProcessAllMessages: boolean; |
Processes all pending messages.
Contrast this with ProcessMessage method, that processes only a single event. Or no event at all (when no events were pending and AllowSuspend = False ). This means that after calling ProcessMessage once, you may have many messages left in the queue (especially mouse move together with key presses typically makes a lot of events). So it's not good to use if you want to react timely to some user requests, e.g. when you do something time-consuming and allow user to break the task with Escape key.
ProcessAllMessages is like calling in a loop something like ProcessMessage(false), ends when ProcessMessage didn't process any message (it's internally returned by ProcessMessage2) or when quit was called (or last window closed).
So ProcessAllMessages makes sure we have processed all pending events, thus we are up-to-date with window system requests.
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procedure Quit; |
Close all open windows, make ProcessMessage return False , finish the Run method (if working), and thus finish the application work.
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procedure Run; |
Run the program using TCastleWindowBase, by doing the event loop. Think of it as just a shortcut for "while ProcessMessage do ;".
Note that this does nothing if OpenWindowsCount = 0, that is there are no open windows. Besides the obvious reason (you didn't call TCastleWindowBase.Open on any window...) this may also happen if you called Close (or Application.Quit) from your window OnOpen / OnResize callback. In such case no event would probably reach our program, and user would have no chance to quit, so Run just refuses to work and exits immediately without any error.
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function BackendName: string; |
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constructor Create(AOwner: TComponent); override; |
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destructor Destroy; override; |
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Properties
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property XDisplayName: string read FXDisplayName write FXDisplayName; |
Set XDisplay name, this will be used for all TCastleWindowBase that will be subsequently initialized by TCastleWindowBase.Open.
Note that this is exposed by GTK even for non-XWindows platforms, but I don't know what it does there.
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property VideoColorBits: integer read FVideoColorBits write FVideoColorBits default 0; |
Color bits per pixel that will be set by next VideoChange call, and that are tried to be used at TCastleWindowBase.Open. Zero means that system default is used.
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property VideoFrequency: Cardinal read FVideoFrequency write FVideoFrequency default 0; |
Video frequency to set in next VideoChange call. Leave as 0 to use system default.
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property OnTimer: TProcedure read FOnTimer write FOnTimer; |
Event called approximately after each TimerMilisec miliseconds. The actual delay may be larger than TimerMilisec miliseconds, depending on how the program (and OS) is busy.
You can of course change TimerMilisec (and OnTimer ) even when some windows are already open.
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property TimerMilisec: Cardinal read FTimerMilisec write FTimerMilisec default 1000; |
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