For purposes of rendering 2D utility text (e.g., FPS display) with OpenGL, I’ve been using glDrawPixels to render a 2D “overlay layer.” The source for the text pixel data is SDL_ttf 2.0.9. Using an example I found somewhere, I did the following: (1) Create an SDL “text” surface with TTF_RenderUNICODE_Blended; (2) Create an SDL “RGB” surface suitable for OpenGL rendering with SDL_CreateRGB surface; (3) Blit the text surface to the RGB surface with SDL_UpperBlit; (4) Render the pixel data in the RGB surface with glDrawPixels. This worked well … until I tried the same thing with SDL 1.3.
With SDL 1.3, no text was rendered. While debugging, I discovered that TTF_RenderUNICODE_Blended was generating good pixel data. SDL_CreateRGBSurface, likewise, created an apparently good SDL surface. However, after the SDL_UpperBlit, the pixel data in the RGB surface was all zeros.
When I saw the format of the pixel data in the text surface (RGBA, 4-byte pixels), I thought why not render the image data right out of the text surface? That works!
Two questions:
Is my solution a reasonable practice or a dangerous practice?
Can anyone venture a guess as to what was wrong with my original approach and SDL 1.3.
That sounds like a bug in SDL 1.3. Can you create a simple test case
and report a bug here? http://bugzilla.libsdl.org/
As for using the text surface directly, that’s totally fine.
Thanks!On Fri, Oct 16, 2009 at 1:15 PM, WaltN wrote:
For purposes of rendering 2D utility text (e.g., FPS display) with OpenGL,
I’ve been using glDrawPixels to render a 2D “overlay layer.” The source for
the text pixel data is SDL_ttf 2.0.9. Using an example I found somewhere, I
did the following: (1) Create an SDL “text” surface with
TTF_RenderUNICODE_Blended; (2) Create an SDL “RGB” surface suitable for
OpenGL rendering with SDL_CreateRGB surface; (3) Blit the text surface to
the RGB surface with SDL_UpperBlit; (4) Render the pixel data in the RGB
surface with glDrawPixels. This worked well … until I tried the same thing
with SDL 1.3.
With SDL 1.3, no text was rendered. While debugging, I discovered that
TTF_RenderUNICODE_Blended was generating good pixel data.
SDL_CreateRGBSurface, likewise, created an apparently good SDL surface.
However, after the SDL_UpperBlit, the pixel data in the RGB surface was all
zeros.
When I saw the format of the pixel data in the text surface (RGBA, 4-byte
pixels), I thought why not render the image data right out of the text
surface? That works!
Two questions:
Is my solution a reasonable practice or a dangerous practice?
Can anyone venture a guess as to what was wrong with my original approach
and SDL 1.3.
That sounds like a bug in SDL 1.3. Can you create a simple test case
and report a bug here? http://bugzilla.libsdl.org/
I will try to reproduce the problem in C. I am writing support for SDL/OpenGL in APL, so, if I gave you my existing code, no one is likely to understand it!
