From 18720665d2b1b48250f2049378cb93eb6e38eaa4 Mon Sep 17 00:00:00 2001
From: Guldoman <giulio.lettieri@gmail.com>
Date: Tue, 14 Mar 2023 16:39:00 +0100
Subject: [PATCH] Use clipping functions provided by SDL (#1426)

---
 src/renderer.c  | 31 ++++++++++++++-----------------
 src/renwindow.c |  6 ++++--
 src/renwindow.h |  1 -
 3 files changed, 18 insertions(+), 20 deletions(-)

diff --git a/src/renderer.c b/src/renderer.c
index 59004bc0..226dbe71 100644
--- a/src/renderer.c
+++ b/src/renderer.c
@@ -378,7 +378,8 @@ double ren_font_group_get_width(RenWindow *window_renderer, RenFont **fonts, con
 
 double ren_draw_text(RenWindow *window_renderer, RenFont **fonts, const char *text, size_t len, float x, int y, RenColor color) {
   SDL_Surface *surface = renwin_get_surface(window_renderer);
-  const RenRect clip = window_renderer->clip;
+  SDL_Rect clip;
+  SDL_GetClipRect(surface, &clip);
 
   const int surface_scale = renwin_surface_scale(window_renderer);
   double pen_x = x * surface_scale;
@@ -386,7 +387,7 @@ double ren_draw_text(RenWindow *window_renderer, RenFont **fonts, const char *te
   int bytes_per_pixel = surface->format->BytesPerPixel;
   const char* end = text + len;
   uint8_t* destination_pixels = surface->pixels;
-  int clip_end_x = clip.x + clip.width, clip_end_y = clip.y + clip.height;
+  int clip_end_x = clip.x + clip.w, clip_end_y = clip.y + clip.h;
 
   RenFont* last = NULL;
   double last_pen_x = x;
@@ -479,28 +480,24 @@ static inline RenColor blend_pixel(RenColor dst, RenColor src) {
 void ren_draw_rect(RenWindow *window_renderer, RenRect rect, RenColor color) {
   if (color.a == 0) { return; }
 
+  SDL_Surface *surface = renwin_get_surface(window_renderer);
   const int surface_scale = renwin_surface_scale(window_renderer);
 
-  /* transforms coordinates in pixels. */
-  rect.x      *= surface_scale;
-  rect.y      *= surface_scale;
-  rect.width  *= surface_scale;
-  rect.height *= surface_scale;
+  SDL_Rect dest_rect = { rect.x * surface_scale,
+                         rect.y * surface_scale,
+                         rect.width * surface_scale,
+                         rect.height * surface_scale };
 
-  const RenRect clip = window_renderer->clip;
-  int x1 = rect.x < clip.x ? clip.x : rect.x;
-  int y1 = rect.y < clip.y ? clip.y : rect.y;
-  int x2 = rect.x + rect.width;
-  int y2 = rect.y + rect.height;
-  x2 = x2 > clip.x + clip.width ? clip.x + clip.width : x2;
-  y2 = y2 > clip.y + clip.height ? clip.y + clip.height : y2;
-
-  SDL_Surface *surface = renwin_get_surface(window_renderer);
-  SDL_Rect dest_rect = { x1, y1, x2 - x1, y2 - y1 };
   if (color.a == 0xff) {
     uint32_t translated = SDL_MapRGB(surface->format, color.r, color.g, color.b);
     SDL_FillRect(surface, &dest_rect, translated);
   } else {
+    // Seems like SDL doesn't handle clipping as we expect when using
+    // scaled blitting, so we "clip" manually.
+    SDL_Rect clip;
+    SDL_GetClipRect(surface, &clip);
+    if (!SDL_IntersectRect(&clip, &dest_rect, &dest_rect)) return;
+
     uint32_t *pixel = (uint32_t *)draw_rect_surface->pixels;
     *pixel = SDL_MapRGBA(draw_rect_surface->format, color.r, color.g, color.b, color.a);
     SDL_BlitScaled(draw_rect_surface, NULL, surface, &dest_rect);
diff --git a/src/renwindow.c b/src/renwindow.c
index 85fd7a07..c700cedf 100644
--- a/src/renwindow.c
+++ b/src/renwindow.c
@@ -61,12 +61,14 @@ static RenRect scaled_rect(const RenRect rect, const int scale) {
 
 void renwin_clip_to_surface(RenWindow *ren) {
   SDL_Surface *surface = renwin_get_surface(ren);
-  ren->clip = (RenRect) {0, 0, surface->w, surface->h};
+  SDL_SetClipRect(surface, NULL);
 }
 
 
 void renwin_set_clip_rect(RenWindow *ren, RenRect rect) {
-  ren->clip = scaled_rect(rect, renwin_surface_scale(ren));
+  SDL_Surface *surface = renwin_get_surface(ren);
+  RenRect sr = scaled_rect(rect, renwin_surface_scale(ren));
+  SDL_SetClipRect(surface, &(SDL_Rect){.x = sr.x, .y = sr.y, .w = sr.width, .h = sr.height});
 }
 
 
diff --git a/src/renwindow.h b/src/renwindow.h
index 8edc03d8..7f08aa2f 100644
--- a/src/renwindow.h
+++ b/src/renwindow.h
@@ -3,7 +3,6 @@
 
 struct RenWindow {
   SDL_Window *window;
-  RenRect clip; /* Clipping rect in pixel coordinates. */
 #ifdef LITE_USE_SDL_RENDERER
   SDL_Renderer *renderer;
   SDL_Texture *texture;