Engine: small fixes to comments regarding color depth in code

Engine/ac/draw.cpp

@@ -2034,7 +2034,7 @@ void tint_image (Bitmap *ds, Bitmap *srcimg, int red, int grn, int blu, int ligh
 
  if ((srcimg->GetColorDepth() != ds->GetColorDepth()) ||
  (srcimg->GetColorDepth() <= 8)) {
- debug_script_warn("Image tint failed - images must both be hi-color");
+ debug_script_warn("Image tint failed - images must both be same color depth and not 8-bit");
  // the caller expects something to have been copied
  ds->Blit(srcimg, 0, 0, 0, 0, srcimg->GetWidth(), srcimg->GetHeight());
  return;
@@ -2261,10 +2261,9 @@ PBitmap draw_room_background(Viewport *view)
 
  // For the sake of software renderer, if there is any kind of camera transform required
  // except screen offset, we tell it to draw on separate bitmap first with zero transformation.
- // There are few reasons for this, primary is that Allegro does not support StretchBlt
- // between different colour depths (i.e. it won't correctly stretch blit 16-bit rooms to
- // 32-bit virtual screen).
- // Also see comment to ALSoftwareGraphicsDriver::RenderToBackBuffer().
+ // There have been few reasons for this in the past, primary being that Allegro does not support
+ // StretchBlt between different colour depths, but that one may be not relevant now.
+ // See Also: comment inside ALSoftwareGraphicsDriver::RenderToBackBuffer().
  const int view_index = view->GetID();
  Bitmap *ds = gfxDriver->GetMemoryBackBuffer();
  // If separate bitmap was prepared for this view/camera pair then use it, draw untransformed

Engine/ac/global_palette.cpp

@@ -25,6 +25,7 @@ extern RGB palette[256];
 void CyclePalette(int strt,int eend) {
  // hi-color game must invalidate screen since the palette changes
  // the effect of the drawing operations
+ // FIXME: this is likely wrong, it should also/instead test the graphic driver capabilities?
  if (game.color_depth > 1)
  invalidate_screen();
 

Engine/gfx/ali3dogl.cpp

@@ -907,17 +907,10 @@ bool OGLGraphicsDriver::GetCopyOfScreenIntoBitmap(Bitmap *destination,
  Rect copy_from = src_rect ? *src_rect : _srcRect;
  if (!at_native_res)
  copy_from = _scaling.ScaleRange(copy_from);
-
- // TODO: following implementation currently only reads GL pixels in 32-bit RGBA.
- // this **should** work regardless of actual display mode because OpenGL is
- // responsible to convert and fill pixel buffer correctly.
- // If you like to support writing directly into 16-bit bitmap, please take
- // care of ammending the pixel reading code below.
- const int read_in_colordepth = 32;
- if (destination->GetColorDepth() != read_in_colordepth || destination->GetSize() != copy_from.GetSize())
+ if (destination->GetColorDepth() != _mode.ColorDepth || destination->GetSize() != copy_from.GetSize())
  {
  if (want_fmt)
- *want_fmt = GraphicResolution(copy_from.GetWidth(), copy_from.GetHeight(), read_in_colordepth);
+ *want_fmt = GraphicResolution(copy_from.GetWidth(), copy_from.GetHeight(), _mode.ColorDepth);
  return false;
  }
 
@@ -946,7 +939,8 @@ bool OGLGraphicsDriver::GetCopyOfScreenIntoBitmap(Bitmap *destination,
  }
 
  // Retrieve the backbuffer pixels
- const int bpp = read_in_colordepth / 8;
+ // NOTE: this is currently hardcoded to read from a 32-bit display mode
+ const int bpp = 32 / 8;
  const int buf_sz = copy_from.GetWidth() * copy_from.GetHeight() * bpp;
  std::vector<uint8_t> buffer(buf_sz);
  glReadPixels(copy_from.Left, copy_from.Top, copy_from.GetWidth(), copy_from.GetHeight(), GL_RGBA, GL_UNSIGNED_BYTE, &buffer.front());