The gl viewport origin is the lower left corner of the window, in d3d
it is the upper right corner. This is corrected when setting the
viewport. However, when we are doing offscreen rendering, this is
reversed. So do not flip the viewport origin when rendering offscreen.
Except with fbos, it is not possible to remove the depth stencil
buffer from the opengl frame buffer, so when the d3d app sets a NULL
depth stencil disable all states that work with the depth stencil
buffer.
This helps performance a bit because the function does not have to
wait for the 2nd read to finish before returning. Only do that if we
have an aux buffer to mess with for free though.
Plain OpenGL does not provide any signed pixel formats, so the
unsigned GL_RGB is used for loading perturbation data into pixel
shaders that use texbem. For correct loading, the signedness has to be
considered.
When drawing processed vertices with the fixed function pipeline the
projection matrix is set up to map y values from 0 to height to 1.0;
-1.0(gl and d3d coord systems are flipped). This moves the y axis to
the bottom of the drawing area. When later on the y inversion matrix
is applied for offscreen rendering, the coordinate system will get
flipped out of the viewport.
This patch sets the Y range up upside down when using offscreen
rendering, so the invymat will flip it to the correct position. This
has to happen before the 0.375 pixel correction.
It was incorrect to disable the scissor test for full surfaces in my
clear patch. With back buffer offscreen rendering the viewport does
not seem to restrict clearing, and with different sizes of depth
stencil and color buffer the final fantasy XI demo seems to expect the
clear to be restricted.
The hwstretch blit code creates a new texture each time it is called
to back up the back buffer and releases it afterwards. It is more
efficient to keep the texture and release it with the surface.
OpenGL AUX buffers provide a way for offscreen rendering which is very
similar to our back buffer "offscreen" rendering emulation. Not all
card support aux buffers, but if they are available they are a nice
present which is easy to use.
Index buffer creation changes the bound gl buffer, thus the state has to
be dirtified, similar to locking.
In an error case the function returned without calling LEAVE_GL().
UpdateSurface has to modify one gl texture unit to bind the texture to
load. To restore the correct properties for drawing gl texture unit 0
is activated and dirtified.
Fix the use of the scissor test in Clear. The rectangle is only set if
a clearing rectangle is used, otherwise the scissor test is disabled
(the pixel ownsership test should take care of the window
boarders). To get the scissor test back to the value the app set up
Clear dirtifies the state(s).
Test how shader constant limits are checked in Set*ShaderConstantF.
The vertex shader tests it based on the limits reported in the caps,
the pixel shader tests tries to find the limit manually because I
could not find a cap structure member specifying the pixel shader
constant limit.
Set*ShaderConstantF returns an error as soon as start or start + count
are bigger than the constant limit.
