[perl-win32-gui-hackers] Bitmap Scolling example.

[Jez W. <je...@je...>]

Hi,

The code below shows an example of using a child window containing a =
bitmap which is scrolled using the scroll bars of the child window. The =
example uses a hooked paint message to pain directly to the child window =
via a memory DC.=20

Assuming there is no problem with this example and people think it's =
useful I'll commit it to the samples folder today.

Cheers,

jez.

=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
#This example creates a scrolling bitmap within another window. This =
example uses
#a hooked event to paint to the window directly, rather than using a =
Graphic
#Control.

use Win32::GUI;
use strict;

#create a new class which stops the WM_ERASEBKGND message from erasing =
the background
my $WC =3D new Win32::GUI::Class(
    -name =3D> "NoFlicker",=20
    -style =3D> 0,
);

#Create the window and child controls.
my $mainwin =3D new Win32::GUI::Window (
    -pos         =3D> [100, 100],
    -size        =3D> [330, 235],
    -name        =3D> "Window",
    -text        =3D> "Bitmap Scroll demo",
    -pushstyle   =3D> WS_CLIPCHILDREN,
    -class       =3D> $WC,
    #NEM Events for this window
    -onResize    =3D> \&Resize,
    -onTerminate =3D> sub {return -1;}
);

$mainwin->AddButton (
    -name        =3D> 'Open',
    -pos         =3D> [205, 20],
    -size        =3D> [110, 20],
    -text        =3D> 'Open Bitmap',
    -onClick     =3D> \&OpenBitmap,
);

#Create a child window with a scroll bars.=20
my $ChildWin =3D new Win32::GUI::Window (
    -parent      =3D> $mainwin,
    -name        =3D> "ChildWin",
    -pos         =3D> [0, 0],
    -size        =3D> [200, 200],
    -popstyle    =3D> WS_CAPTION | WS_SIZEBOX,
    -pushstyle   =3D> WS_CHILD | WS_CLIPCHILDREN,
    -pushexstyle =3D> WS_EX_CLIENTEDGE,
    -class       =3D> $WC,
    -hscroll     =3D> 1,
    -vscroll     =3D> 1,
    -onScroll    =3D> \&Scroll,
);

#hook into the paint event of the child window
$ChildWin->Hook(15, \&Paint);

#Create a memory DC compatible with the child window DC
my $memdc=3D$ChildWin->GetDC->CreateCompatibleDC();
#Define global variables
my $bitmap;        #will hold the bitmap

#show both windows and enter the Dialog phase.
$mainwin->Show();
$ChildWin->Show();
Win32::GUI::Dialog();

sub Paint {
  #Paint event handler, called when ever the window needs to be =
redrawn/painted
  return unless $bitmap;
  #tell windows that we are starting to paint
  $ChildWin->BeginPaint;
  #get the DC of the child window
  my $dc=3D$ChildWin->GetDC;
  #Performa a bit block transfer of the memory DC into the child window =
DC
  #The cordinates are based upon the possition of the scroll bars
  $dc->BitBlt(0, 0, =
$ChildWin->Width,$ChildWin->Height,$memdc,$ChildWin->ScrollPos(0),$ChildW=
in->ScrollPos(1));
  #tell windows that we have finished painting.
  $ChildWin->EndPaint;
}


sub Resize {
  #Resize handler
  my ($width, $height) =3D ($mainwin->GetClientRect)[2..3];
  $mainwin->Open->Left($width-120);
  #Resize the child window and set the scroll bar page of each scroll =
bar.
  #This has the effect of increasing/decreasing the size of the bar =
within the scroll bar
  #as the window is resized.
  $ChildWin->Resize($width-150,$height);
  $ChildWin->ScrollPage(0,$ChildWin->Width);
  $ChildWin->ScrollPage(1,$ChildWin->Height);
}

sub OpenBitmap {
  #Function to load in the bitmap
  my $file =3D Win32::GUI::GetOpenFileName(
                   -owner =3D> $mainwin,
                   -hidereadonly =3D> 0,
                   -title  =3D> "Open an bitmap file",
                   -filter =3D> ['Bitmaps' =3D> '*.bmp',
                               'All files'    =3D> '*.*',
                              ],               =20
                   );
  $bitmap=3Dnew Win32::GUI::Bitmap($file);  =20
  if ($bitmap) {
    #if we have a valid bitmap, get the dimentions
    my ($width,$height)=3D$bitmap->Info();
    #select the bitmap into the memory DC so it can be maniplated later.
    $memdc->SelectObject($bitmap);
    #set the scroll bar range and position based upon the height and =
width of the bitmap.
    $ChildWin->ScrollRange(1,0,$height+20); #add 20 for the scroll bar
    $ChildWin->ScrollRange(0,0,$width+20);
    $ChildWin->ScrollPage(0,$ChildWin->Width);
    $ChildWin->ScrollPage(1,$ChildWin->Height);
    #set the scroll bars to 0.
    $ChildWin->ScrollPos(0,0);  =20
    $ChildWin->ScrollPos(1,0);
    $ChildWin->InvalidateRect(0); #invalidate the child window so =
windows triggers the paint event
  }
}

sub Scroll {
  #Scroll event handler. We have to explicitly "move" the scroll bars.
  #Once they have been moved, we repaint the window.
  my($win,$scrollbar, $operation, $position) =3D @_;
  if($operation =3D=3D SB_THUMBTRACK) {
    $win->ScrollPos($scrollbar,$position);
    }
  elsif($operation =3D=3D SB_LINEDOWN) {
    $win->ScrollPos($scrollbar,$win->ScrollPos($scrollbar)+1);
  }
  elsif($operation =3D=3D SB_LINEUP) {
    $win->ScrollPos($scrollbar,$win->ScrollPos($scrollbar)-1);
  }
  elsif($operation =3D=3D SB_PAGEDOWN) {
    $win->ScrollPos($scrollbar,$win->ScrollPos($scrollbar) + =
$win->ScrollPage($scrollbar));
  }
  elsif($operation =3D=3D SB_PAGEUP) {
    $win->ScrollPos($scrollbar,$win->ScrollPos($scrollbar) - =
$win->ScrollPage($scrollbar));
  }
 #invalidate the child window so windows triggers the paint event
 $win->InvalidateRect(0);
}