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From Wojciech Lewandowski, "As promised I prepared a patch to expose WGL_SWAP_METHOD / PFD_SWAP_METHOD selection via GraphicsContext::Traits. Since Traits don't define any enums (I guess to be simple to use) I tried to keep it that way and have added two boolean values: swapCopy & swapExchange. It is somewhat similar approach to GDI PixelFormatDescription were both options can be present together. Feel free to replace it with enum if you find it more appropriate.

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I also uderstand that there is a need to select system wide default  method and have also modified DisplaySettings to contain swapMethod parameter. Swap method in Traits uses value set in DisplaySettings as default. Proper environment and command line args were added.  Its possible to define default DeisplaySettings swap method in standard way via system flags or with comand line.

Env Vars:
    OSG_SWAP_METHOD  = DEFAULT | COPY | EXCHANGE
or Command Line:
    --swap-method   DEFAULT | COPY | EXCHANGE

I also added handling of WM_ERASEBKGND in GraphicsWindowWin32. It may be unneccessary but code should be safer this way than without handling it.  I have placed a comment explaining the reason above the change.

Changes were made against today trunk.

PS. I tested only Windows code. I briefly checked X11 & Cocoa files but have not noticed SwapMethod to be used there.
"
This commit is contained in:
Robert Osfield 2010-10-01 18:02:24 +00:00
parent c294814e95
commit f81a9eff50
1 changed files with 39 additions and 2 deletions
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41
src/osgViewer/GraphicsWindowWin32.cpp
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@ -1474,7 +1474,30 @@ static void PreparePixelFormatSpecifications( const osg::GraphicsContext::Traits
if (traits.doubleBuffer)
{
attributes.enable(WGL_DOUBLE_BUFFER_ARB);
if (allowSwapExchangeARB) attributes.set(WGL_SWAP_METHOD_ARB, WGL_SWAP_EXCHANGE_ARB);
switch ( traits.swapMethod )
{
case osg::DisplaySettings::SWAP_COPY:
attributes.set(WGL_SWAP_METHOD_ARB, WGL_SWAP_COPY_ARB);
break;
case osg::DisplaySettings::SWAP_EXCHANGE:
attributes.set(WGL_SWAP_METHOD_ARB, WGL_SWAP_EXCHANGE_ARB);
break;
case osg::DisplaySettings::SWAP_UNDEFINED:
attributes.set(WGL_SWAP_METHOD_ARB, WGL_SWAP_UNDEFINED_ARB);
break;
case osg::DisplaySettings::SWAP_DEFAULT:
// Wojtek Lewandowski 2010-09-28:
// Keep backward compatibility if no method is selected via traits
// and let wglSwapExchangeARB flag select swap method.
// However, I would rather remove this flag because its
// now redundant to Traits::swapMethod and it looks like
// WGL_SWAP_EXCHANGE_ARB is the GL default when no WGL_SWAP attrib is given.
// To be precise: At least on Windows 7 and Nvidia it seems to be a default.
if ( allowSwapExchangeARB )
attributes.set(WGL_SWAP_METHOD_ARB, WGL_SWAP_EXCHANGE_ARB);
break;
}
}
if (traits.alpha) attributes.set(WGL_ALPHA_BITS_ARB, traits.alpha);
@ -1503,7 +1526,9 @@ static int ChooseMatchingPixelFormat( HDC hdc, int screenNum, const WGLIntegerAt
1, // version number
PFD_DRAW_TO_WINDOW | // support window
PFD_SUPPORT_OPENGL | // support OpenGL
(_traits->doubleBuffer ? PFD_DOUBLEBUFFER : NULL), // double buffered ?
(_traits->doubleBuffer ? PFD_DOUBLEBUFFER : NULL) | // double buffered ?
(_traits->swapMethod == osg::DisplaySettings::SWAP_COPY ? PFD_SWAP_COPY : NULL) |
(_traits->swapMethod == osg::DisplaySettings::SWAP_EXCHANGE ? PFD_SWAP_EXCHANGE : NULL),
PFD_TYPE_RGBA, // RGBA type
_traits->red + _traits->green + _traits->blue, // color depth
_traits->red ,0, _traits->green ,0, _traits->blue, 0, // shift bits ignored
@ -2306,6 +2331,18 @@ LRESULT GraphicsWindowWin32::handleNativeWindowingEvent( HWND hwnd, UINT uMsg, W
switch(uMsg)
{
// Wojtek Lewandowski 2010-09-28:
// All web docs on Windows Aero and OpenGL compatibiltiy
// suggest WM_ERASEBKGND should be handled with non NULL value return.
// This sugesstion may be irrelevant for our window class
// as default brush pattern is not set so erase flag is forwarded to WM_PAINT
// and gets ignored when WM_PAINT is handled.
// But it will certainly be safer and not make things worse
// if we handle this message to be sure everything is done as suggested.
case WM_ERASEBKGND :
return TRUE;
break;
/////////////////
case WM_PAINT :
/////////////////