SetLogicalPage procedure

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Standard Units

Graph Unit

Graph Unit Procedures and Functions

SetLogicalPage procedure

Targets: MS-DOS, Win32

Graph Unit

Sets the logical page size. The SX and SY values are the new logical size.

Declaraton:

procedure SetLogicalPage(SX, SY: Word);

Remarks:
Many SVGA adapters support logical pages. A logical page can exceed the size of the physical screen. For instance, it is possible to install a logical page 1280 x 480 with a screen of physical resolution 640x480. In this case only half the logical page will be seen on the screen. Logical pages are used for hardware scrolling. The maximum size logical pages depend on the SVGA adapter and the size of the video memory. Use the function GetLogicalPage to get the current logical page size. Remember that the number of available graphic pages depends on the logical page size. Thus SetLogicalPage influences the number of available graphic pages and resets viewport to the whole logical page size. Keep in mind, that SX and SY can't be less than the physical screen size. Here is an example of use of the logical page:

// This example sets a logical page 1280x600
// and performs hardware scrolling
// VESA-compatible SVGA card with 1Mb required
//
uses Graph,Crt;
var
  ErrorCode,i: Longint;
  SX, SY: Word;
begin
  // setup SVGA mode 640x480x256
  SetSVGAMode(640, 480, 8, LfbOrBanked);
  ClearDevice;
  if GraphResult <> 0 then begin
    ErrorCode:=GraphResult;
    CloseGraph;
    Writeln(GraphErrorMsg(ErrorCode));
  end;
  // setup logical page 1280x600
  SetLogicalPage(1280, 600);
  // check logical page size
  GetLogicalPage(SX, SY);
  if (SX = 640) and (SY = 480) then begin 
    CloseGraph;
    Writeln(' Logical pages not supported...');
  end;
  // draw on logical page
  SetLineStyle(SolidLn, 0, ThickWidth);
  SetColor(clRed);
  Line(0, 0, GetMaxX, GetMaxY);
  Line(GetMaxX, 0, 0, GetMaxY);
  SetColor(clWhite);
  Rectangle(0, 0, GetMaxX, GetMaxY);
  // scroll the screen left
  for i := 0 to (SX - 640) div 4 do
    SetScreenStart(i * 4, 0, True);
  // scroll the screen up
  for i := 0 to (SY - 480) div 4 do
    SetScreenStart(SX - 640, i * 4, True);
  // scroll the screen right
  for i := (SX - 640) div 4 downto  0 do
    SetScreenStart(i * 4, SY - 480, True);
  // scroll the screen down
  for  i := (SY - 480) div 4 downto 0 do
    SetScreenStart(0, i * 4, True);
  // Wait a key
  ReadKey;
  // Close Graph and restore old video mode
  CloseGraph;
end.


SetLineStyle procedure	Table of Content	SetNormalMode procedure

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