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SDL 2 Blitting TTF_RenderText_Solid onto surface
YouCOde


Joined: 19 May 2014
Posts: 5
Post Posted: Mon May 19, 2014 10:36 pm
Hello and thanks to all who will read this post, it is my first so I'll try to explain well.
So, I am stuck on a pretty simle problem but haven't found the right answer yet: I create a surface with TTF_RenderText_Solid, and then try to Blit it onto a monotone surface, then convert the resulting surface to a Texture, and rendering to screen. Only, the text doesn't show, on my screen i get the "box", but not the text that should have been blitted on it... Help! (checked errors and i do not get any)

Code:

SDL_Color paint={0,0,0};
    SDL_Surface *Text;
    Text=TTF_RenderText_Solid(Font,"HELLO", paint);

SDL_Surface *Box=SDL_CreateRGBSurface(0,60,30,32,0,0,0,0);
    Uint32 color=SDL_MapRGB(Box->format,200,200,200);
    SDL_FillRect(Box,NULL,color);
SDL_Rect Rect={0-0-0-0};

SDL_BlitSurface(Text, NULL, Box,NULL );

    SDL_Texture *Texture;
    Texture=SDL_CreateTextureFromSurface(Renderer,Box);

    SDL_RenderCopy(Renderer,Texture,NULL,&Rect);
lorin


Joined: 27 Dec 2010
Posts: 17
Post Posted: Tue May 20, 2014 12:58 pm
Are you sure with this line:

Code:
SDL_Rect Rect={0-0-0-0};


Try to use NULL as dstrect:

Code:
SDL_RenderCopy(Renderer,Texture,NULL, NULL);
Tried a lot of different rectangle sizes, and none at all.
YouCOde


Joined: 19 May 2014
Posts: 5
Post Posted: Tue May 20, 2014 6:52 pm
Yes i did, and didn't get anything better!
The scales do not matter at the point, it just fills the whole screen, but no text appears either...
Thanks for the quick reply though Very Happy
Re: SDL 2 Blitting TTF_RenderText_Solid onto surface
YouCOde


Joined: 19 May 2014
Posts: 5
Post Posted: Tue May 20, 2014 7:23 pm
Tried again, and again, but to no avail!
I modified the rectangle definition, i think it was c++ type definitions? And also made the destination surface of the blit an RGBA surface...

Code:
SDL_Color paint={0,0,0};
    SDL_Surface *Text;
    Text=TTF_RenderText_Solid(Font,"HELLO", paint);

    SDL_Surface *Box=SDL_CreateRGBSurface(0,60,30,32,0,0,0,0);
    Uint32 color=SDL_MapRGBA(Box->format,0,200,0,255);
    ErrorsNegativeNumber(SDL_FillRect(Box,NULL,color));
    SDL_Rect Rect={50,50,60,30};

    SDL_BlitSurface(Text, NULL, Box,NULL );

    SDL_Texture *Texture;
    ErrorsNull(Texture=SDL_CreateTextureFromSurface(Renderer,Box));

    ErrorsNegativeNumber(SDL_RenderCopy(Renderer,Texture,NULL,&Rect));

    SDL_RenderPresent(Renderer);
Starg


Joined: 28 Mar 2014
Posts: 22
Post Posted: Tue May 20, 2014 9:39 pm
Have you tried changing the first line to a colour other than black?
Can I ask why you blit to another surface and the a texture? Rather than just converting straight to a texture?
Starg


Joined: 28 Mar 2014
Posts: 22
Post Posted: Wed May 21, 2014 1:38 am
Also, you should set your colours with 4 parameters, otherwise you could be drawing with zero alpha. E.g paint = {255,255,255,255} for white or paint={0,0,0,255} for black.
mr_tawan


Joined: 13 Jan 2014
Posts: 161
Post Posted: Wed May 21, 2014 10:58 am
Just in case, did you enable/set the blend mode (https://wiki.libsdl.org/SDL_SetRenderDrawBlendMode) before the RenderCopy call ?
mr_tawan


Joined: 13 Jan 2014
Posts: 161
Post Posted: Wed May 21, 2014 1:16 pm
lorin wrote:
Are you sure with this line:

Code:
SDL_Rect Rect={0-0-0-0};




Looks like C++11's initialized list to me. Although effectively it's similar to :-

Code:
SDL_Rect Rect={0};


As 0-0-0-0 = 0. The others member are left uninitialized, or undefined.

mr_tawan wrote:
Just in case, did you enable/set the blend mode (https://wiki.libsdl.org/SDL_SetRenderDrawBlendMode) before the RenderCopy call ?


Guess I misread the thread.

Anyway have you tried setting all 4 members of paint ? Something like
Code:
SDL_Color paint={0,0,0,255};

The last one is alpha(translucency) byte of the color. I think it's ordered as rgba. Just in case I'm wrong, be set it to white

Code:
SDL_Color paint={255,255,255,255};


As the order is now not relevant (everything is 255).
YouCOde


Joined: 19 May 2014
Posts: 5
Post Posted: Thu May 22, 2014 4:00 pm
Ok, i checked all the things you pointed out, the rect values, the alpha channel of the color struct, and the color codes, but the text still does not show. I'd like to do this so it will be easier to only handle one texture after the blit, but for now what i will do is make two textures and render them on top of one another.
So, the text doesn't show after the blit, and if i instead blit the monotone surface on top of the text surface, then make a texture from that and render it, it shows the text, with a weird small square on the top right of it... It would be really nice to have just one texture to render around, than two!
Thank you!
mr_tawan


Joined: 13 Jan 2014
Posts: 161
Post Posted: Thu May 22, 2014 9:06 pm
I don't see why would you need 2 texture for that.

Anyway I had spent an hour creating the test, and looks like it could be archive with only 1 texture. The complete code is below. It's a bit long, btw.

Code:

#include "SDL.h"
#include "SDL_ttf.h"

int main(int argc, char** args)
{
  SDL_Color color{0xFF, 0xFF, 0xFF, 0xFF};

  SDL_Init(SDL_INIT_EVERYTHING);
  SDL_Window *pWindow;
  SDL_Renderer *pRenderer;

  SDL_CreateWindowAndRenderer(800,
                              600,
                              SDL_WINDOW_OPENGL,
                              &pWindow,
                              &pRenderer);

  SDL_SetRenderDrawColor(pRenderer, 0, 0, 0, 0);

  TTF_Init();
  TTF_Font *pFont = TTF_OpenFont("./TS-Kaewpet-NP/TS-kaewpet Bold-NP.ttf", 64);
  SDL_Surface *pSurface = TTF_RenderText_Solid(pFont, "This is a Test Text", color);
  SDL_Texture *pTexture = SDL_CreateTextureFromSurface(pRenderer, pSurface);

  while(true)
  {
    SDL_RenderClear(pRenderer);
    SDL_Event event;
    while (SDL_PollEvent(&event))
    {
      if(event.type == SDL_QUIT) goto quit;
    }

    SDL_RenderCopy(pRenderer, pTexture, NULL, NULL);

    SDL_RenderPresent(pRenderer);
    SDL_Delay(33);
  }

quit:
  TTF_Quit();
  SDL_DestroyRenderer(pRenderer);
  SDL_DestroyWindow(pWindow);

  SDL_Quit();

  return 0;
}


Tested on Arch Linux 64 bit, GNOME 3.12, SDL2_2.0.3 and SDL2_ttf_2.0.12. What is your platform, btw?

One more thing, I'm working on a text rendering lib using FreeType2 and Harfbuzz. Glyph is rendered directly, no surface or texture (though it could be rendered to texture using render target). I'll let people here know when it's matured enough.
YouCOde


Joined: 19 May 2014
Posts: 5
Post Posted: Fri May 23, 2014 5:14 am
Thank you mr_tawan, but my problem is with blitting a text surface on top of another surface. When I do this, it is like the text surface disappears during the blit. More specifically, the test surface isn't a picture, just a unicolor surface colored in with SDL_FillRect.
Thank you again!

Windows 8 64bit codeblocks mingw32
SDL 2 Blitting TTF_RenderText_Solid onto surface
Jonny D


Joined: 12 Sep 2009
Posts: 932
Post Posted: Fri May 23, 2014 1:24 pm
If you're blitting RGBA SDL_Surfaces onto each other, then you should set the *surface* blend mode.  Most of SDL's blend modes will preserve the destination alpha (which is 0 for new RGBA surfaces, so you don't see anything at all).  Specifically, try SDL_SetSurfaceBlendMode(surface, SDL_BLENDMODE_NONE): https://wiki.libsdl.org/SDL_SetSurfaceBlendMode



Jonny D





On Fri, May 23, 2014 at 1:14 AM, YouCOde wrote:
Quote:
Thank you mr_tawan, but my problem is with blitting a text surface on top of another surface. When I do this, it is like the text surface disappears during the blit. More specifically, the test surface isn't a picture, just a unicolor surface colored in with SDL_FillRect.
Thank you again!

Windows 8 64bit codeblocks mingw32


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