mesa: adjust glBitmap coords by a small epsilon

Fixes problem with bitmaps jumping around by one pixel depending on window
size.  The rasterpos is often X.9999 instead of X+1.
Run progs/redbook/drawf and resize window to check.

Cherry picked from gallium-0.1 branch

diff --git a/src/mesa/main/drawpix.c b/src/mesa/main/drawpix.c
index 4f28766..fde9338 100644 (file)
--- a/src/mesa/main/drawpix.c
+++ b/src/mesa/main/drawpix.c
@@ -374,8 +374,9 @@ _mesa_Bitmap( GLsizei width, GLsizei height,
 
    if (ctx->RenderMode == GL_RENDER) {
       /* Truncate, to satisfy conformance tests (matches SGI's OpenGL). */
-      GLint x = IFLOOR(ctx->Current.RasterPos[0] - xorig);
-      GLint y = IFLOOR(ctx->Current.RasterPos[1] - yorig);
+      const GLfloat epsilon = 0.0001;
+      GLint x = IFLOOR(ctx->Current.RasterPos[0] + epsilon - xorig);
+      GLint y = IFLOOR(ctx->Current.RasterPos[1] + epsilon - yorig);
 
       if (ctx->Unpack.BufferObj->Name) {
          /* unpack from PBO */