proposed fix: set curr_src.h is to bottom_height before drawing bottom edges / corners in SDL_RenderTexture9Grid, to avoid issue where inadvertently using top height if the npatch existed on a larger texture than the drawn edge would cause too many pixels to be included in the bottom part of the render.

src/render/SDL_render.c

@@ -4426,6 +4426,7 @@ bool SDL_RenderTexture9Grid(SDL_Renderer *renderer, SDL_Texture *texture, const
 
     // Lower-right corner
     curr_src.y = srcrect->y + srcrect->h - bottom_height;
+    curr_src.h = bottom_height;
     curr_dst.y = dstrect->y + dstrect->h - dst_bottom_height;
     curr_dst.h = dst_bottom_height;
     if (!SDL_RenderTexture(renderer, texture, &curr_src, &curr_dst)) {
@@ -4474,6 +4475,7 @@ bool SDL_RenderTexture9Grid(SDL_Renderer *renderer, SDL_Texture *texture, const
 
     // Bottom
     curr_src.y = srcrect->y + srcrect->h - bottom_height;
+    curr_src.h = bottom_height;
     curr_dst.y = dstrect->y + dstrect->h - dst_bottom_height;
     curr_dst.h = dst_bottom_height;
     if (!SDL_RenderTexture(renderer, texture, &curr_src, &curr_dst)) {