- 4.37.1.9. -
Table of Contents
4. Standard Units
4.37. Graph - Graph unit
4.37.1. Graph Unit Types, Constants, and Variables
4.37.1.9. GraphWndProc
4.37.1.9. GraphWndProc
Targets: Win32 only
Graph Unit
A function variable that processes the system messages
sent to the graphical window.
Declaration:
var GraphWndProc: ^function (
Window: HWND;
Mess,
WParam,
LParam: LongInt): LongInt := nil;
Remarks:
Assign your own callback function to the GraphWndProc variable
to process any message sent to the graphical window.
Example:
uses
CRT, Windows, Messages, Graph;
{ Draws a message box }
procedure ShowBox;
begin
SetFillColor(Random(256));
Bar3D(200, 180, 440, 280, 0, FALSE);
SetTextJustify(CenterText, CenterText);
SetColor(clBlack);
OutTextXY(321, 231, 'Click Here');
SetColor(clWhite);
OutTextXY(320, 230, 'Click Here');
end;
{ A custom message handler}
function MyWndProc(Window: HWND; Mess, WParam, LParam: LongInt): LongInt;
begin
if (Mess = WM_LBUTTONDOWN) then
if (LOWORD(lParam) > 200) and
(LOWORD(lParam) < 440) and
(HIWORD(lParam) > 180) and
(HIWORD(lParam) < 280) then
ShowBox
else
Beep(0, 0);
end;
{ Main program }
begin
GraphWndProc := @MyWndProc; // Install a custom message handler
SetSVGAMode(640, 480, 8, 0); // Set desired video mode
ShowCursor(TRUE); // A custom message handler
ShowBox; // Show a message box
ReadKey; // Wait for any key
end.
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