gfx: Clamp texture size larger than GL_MAX_TEXTURE_SIZE

This prevents glTexImage2D() from failing and resulting in an invalid
texture if a width or height specified in sact2.SP_Create() is greater
than GL_MAX_TEXTURE_SIZE.

It is very rare and is probably a programming error in the game script.
If the resulting texture is used for rendering, it may mess up the
screen, but at least it won't crash.

Fixes https://github.com/kichikuou/xsystem4-android/issues/4.

src/video.c

@@ -65,6 +65,7 @@ static struct shader default_shader;
 
 GLuint main_surface_fb;
 struct texture main_surface;
+static GLint max_texture_size;
 
 static GLchar *read_shader_file(const char *path)
 {
@@ -163,6 +164,8 @@ static int gl_initialize(void)
 
 	glBindVertexArray(0);
 
+	glGetIntegerv(GL_MAX_TEXTURE_SIZE, &max_texture_size);
+
 	return 0;
 }
 
@@ -480,6 +483,14 @@ void gfx_init_texture_with_cg(struct texture *t, struct cg *cg)
 
 void gfx_init_texture_rgba(struct texture *t, int w, int h, SDL_Color color)
 {
+	if (w > max_texture_size) {
+		WARNING("Texture width %d exceeds maximum texture size %d", w, max_texture_size);
+		w = max_texture_size;
+	}
+	if (h > max_texture_size) {
+		WARNING("Texture height %d exceeds maximum texture size %d", h, max_texture_size);
+		h = max_texture_size;
+	}
 	// create pixel data
 	int c = SDL_MapRGBA(sdl.format, color.r, color.g, color.b, color.a);
 	uint32_t *pixels = xmalloc(sizeof(uint32_t) * w * h);
@@ -493,6 +504,14 @@ void gfx_init_texture_rgba(struct texture *t, int w, int h, SDL_Color color)
 
 void gfx_init_texture_rgb(struct texture *t, int w, int h, SDL_Color color)
 {
+	if (w > max_texture_size) {
+		WARNING("Texture width %d exceeds maximum texture size %d", w, max_texture_size);
+		w = max_texture_size;
+	}
+	if (h > max_texture_size) {
+		WARNING("Texture height %d exceeds maximum texture size %d", h, max_texture_size);
+		h = max_texture_size;
+	}
 	uint8_t *pixels = xmalloc(w*h*3);
 	for (int i = 0; i < w*h; i++) {
 		pixels[i*3+0] = color.r;