OpenGLControl in ScrollBox with ScrollBar.Tracking
lazarus / 70-OpenGL

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creaothceann · 2017-03-07 00:04

I'm using an OpenGLControl for displaying OpenGL graphics. The Control
is in a ScrollBox whose Horz/VertScrollBar.Tracking properties are
enabled. This means that the OpenGLControl moves while the scroll bar
is moved, and not only when the mouse button is released.
Unfortunately this creates a strange "corruption" effect. (Maybe it's
related to this problem?) Setting the form, the ScrollBox and the
OpenGLControl's DoubleBuffered properties doesn't help.

I know I could probably simulate the ScrollBox with separate
scrollbars, but maybe there is an easier way?

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i unit
U_Form_Main;  interfaceuses Classes, Controls, Forms, GL, Graphics,
OpenGLContext, SysUtils;  type {TForm_Main} TForm_Main = class(TForm) 
      procedure GUI_Form_OnCreate        (Sender : TObject);       
procedure GUI_OpenGLControl_OnClick(Sender : TObject);       
procedure GUI_OpenGLControl_OnPaint(Sender : TObject);        private 
      _OpenGLControl : TOpenGLControl;        _ScrollBox     :
TScrollBox;        end;  var Form_Main :
TForm_Main;  implementation  {$R *.lfm}  {TForm_Main}  procedure
TForm_Main.GUI_Form_OnCreate(Sender : TObject);beginCaption :=
'0';DoubleBuffered := True;_ScrollBox     :=
TScrollBox.Create(Self);with _ScrollBox do begin        Parent       
:= Self;        Align          := alClient;        Color          :=
clAppWorkspace;        DoubleBuffered := True;end;_OpenGLControl :=
TOpenGLControl.Create(_ScrollBox);with _OpenGLControl do begin       
AutoResizeViewport := True;        DoubleBuffered     := True;       
Parent             := _ScrollBox;        Left               := 0;    
  Top                := 0;        Width              := Screen.Width; 
      Height             := Screen.Height;        MultiSampling    
 := 4;        OnClick            := @GUI_OpenGLControl_OnClick;      
OnPaint            := @GUI_OpenGLControl_OnPaint;       
Invalidate;end;end;  procedure
TForm_Main.GUI_OpenGLControl_OnClick(Sender : TObject);beginwith
_ScrollBox do begin        Tag := Tag XOR 1;        Self.Caption :=
IntToStr(Tag);        HorzScrollBar.Tracking := ByteBool(Tag);       
VertScrollBar.Tracking := HorzScrollBar.Tracking;end;end;  procedure
TForm_Main.GUI_OpenGLControl_OnPaint(Sender :
TObject);beginglClearColor(0.27, 0.53, 0.71,
1.0);glClear(GL_COLOR_BUFFER_BIT OR
GL_DEPTH_BUFFER_BIT);glLoadIdentity;glBegin(GL_TRIANGLE_STRIP);      
glColor3F(0, 0, 1);  glVertex3F(-1.0,  1.0, -1.0);        glColor3F(1,
0, 0);  glVertex3F(-1.0, -1.0, -1.0);        glColor3F(0, 1, 1);
 glVertex3F( 1.0,  1.0,  1.0);        glColor3F(1, 1, 0);  glVertex3F(
1.0, -1.0,  1.0);glEnd;_OpenGLControl.SwapBuffers;end;  end.
(This version of the code dynamically allocates the ScrollBox and the
OpenGLControl so that it's clear what settings are used.)

Click on the OpenGLControl to enable the ScrollBar.Tracking.