render: Add SDL_RenderDebugText().

Fixes #11201.

include/SDL3/SDL_render.h

@@ -2464,6 +2464,57 @@ extern SDL_DECLSPEC bool SDLCALL SDL_SetRenderVSync(SDL_Renderer *renderer, int
  */
 extern SDL_DECLSPEC bool SDLCALL SDL_GetRenderVSync(SDL_Renderer *renderer, int *vsync);
 
+/**
+ * The size, in pixels, of a single SDL_RenderDebugText() character.
+ *
+ * The font is monospaced and square, so this applies to all characters.
+ *
+ * \since This macro is available since SDL 3.1.5.
+ *
+ * \sa SDL_RenderDebugText
+ */
+#define SDL_DEBUG_TEXT_FONT_CHARACTER_SIZE 8
+
+/**
+ * Draw debug text to an SDL_Renderer.
+ *
+ * This function will render a string of text to an SDL_Renderer. Note that
+ * this is a convenience function for debugging, with severe limitations, and
+ * not intended to be used for production apps and games.
+ *
+ * Among these limitations:
+ *
+ * - It accepts UTF-8 strings, but will only renders ASCII characters.
+ * - It has a single, tiny size (8x8 pixels). One can use logical
+ *   presentation or scaling to adjust it, but it will be blurry.
+ * - It uses a simple, hardcoded bitmap font. It does not allow different
+ *   font selections and it does not support truetype, for proper scaling.
+ * - It does no word-wrapping and does not treat newline characters as a line
+ *   break. If the text goes out of the window, it's gone.
+ *
+ * For serious text rendering, there are several good options, such as
+ * SDL_ttf, stb_truetype, or other external libraries.
+ *
+ * On first use, this will create an internal texture for rendering glyphs.
+ * This texture will live until the renderer is destroyed.
+ *
+ * The text is drawn in the color specified by SDL_SetRenderDrawColor().
+ *
+ * \param renderer the renderer which should draw a line of text.
+ * \param x the x coordinate where the top-left corner of the text will draw.
+ * \param y the y coordinate where the top-left corner of the text will draw.
+ * \param str the string to render.
+ * \returns true on success or false on failure; call SDL_GetError() for more
+ *          information.
+ *
+ * \threadsafety You may only call this function from the main thread.
+ *
+ * \since This function is available since SDL 3.1.5.
+ *
+ * \sa SDL_DEBUG_TEXT_FONT_CHARACTER_SIZE
+ */
+extern SDL_DECLSPEC bool SDLCALL SDL_RenderDebugText(SDL_Renderer *renderer, float x, float y, const char *str);
+
 /* Ends C function definitions when using C++ */
 #ifdef __cplusplus
 }