Fixed an issue with clipping the render rectangle

src/GameEngine.c

@@ -213,47 +213,82 @@ WindowDrawingArea get_window_drawing_area() {
   return GameEngine.window.drawing_area;
 }
 
-void fill_rectangle(float x, float y, float w, float h, SDL_Color color) {
-  fill_rect(GameEngine.window.renderer, color, x, y, w, h);
+void fill_rectangle(RenderRect rect, SDL_Color color) {
+  fill_rect(GameEngine.window.renderer, color, rect.x, rect.y, rect.width,
+            rect.height);
 }
 
-void clip_render_rect_to_drawing_area(SDL_FRect *rect) {
+void clip_source_rect_to_drawing_area(RenderRect *src, RenderRect *dest) {
   WindowDrawingArea area = get_window_drawing_area();
 
   // If the rectangle is completely out of bounds, set its width and height to 0
-  if (rect->x > area.x + area.width || rect->x + rect->w < area.x ||
-      rect->y > area.y + area.height || rect->y + rect->h < area.y) {
-    rect->w = 0.0f;
-    rect->h = 0.0f;
+  if (dest->x > area.x + area.width || dest->x + dest->width < area.x ||
+      dest->y > area.y + area.height || dest->y + dest->height < area.y) {
+    src->width = 0.0f;
+    src->height = 0.0f;
     return;
   }
 
-  float x_diff = 0.0f;
-  float y_diff = 0.0f;
+  float x_offset = 0.0f;
+  float y_offset = 0.0f;
+  float x_clip = 0.0f;
+  float y_clip = 0.0f;
 
   // If the rectangle is partially out of the horizontal bounds of the drawing
   // area, calculate how much of its width will be clipped
-  if (rect->x < area.x) {
-    x_diff = area.x - rect->x;
-    rect->x += x_diff;
-  } else if (rect->x + rect->w > area.x + area.width) {
-    x_diff = (rect->x + rect->w) - (area.x + area.width);
+  if (dest->x < area.x) {
+    // When an object goes out of the left border of the screen, we need to both
+    // clip and offset the source and destination rectangles to ensure that the
+    // object is rendered properly
+    x_clip = x_offset = area.x - dest->x;
+  } else if (dest->x + dest->width > area.x + area.width) {
+    x_clip = (dest->x + dest->width) - (area.x + area.width);
   }
 
   // If the rectangle is partially out of the vertical bounds of the drawing
   // area, calculate how much of its height will be clipped
-  if (rect->y < area.y) {
-    y_diff = area.y - rect->y;
-    rect->y += y_diff;
-  } else if (rect->y + rect->h > area.y + area.height) {
-    y_diff = (rect->y + rect->h) - (area.y + area.height);
+  if (dest->y < area.y) {
+    // When an object goes out of the top border of the screen, we need to both
+    // clip and offset the source and destination rectangles to ensure that the
+    // object is rendered properly
+    y_clip = y_offset = area.y - dest->y;
+  } else if (dest->y + dest->height > area.y + area.height) {
+    y_clip = (dest->y + dest->height) - (area.y + area.height);
   }
 
-  rect->w -= x_diff;
-  rect->h -= y_diff;
+  // Offset and clipping of source rectangle needs to be calculated based on the
+  // ratio of the x_clip and y_clip variables to the width and height of the
+  // destination rectangle respectively. This is because the source rectangle's
+  // width and height might be different from the destination's
+  src->x += ((x_offset / dest->width) * src->width);
+  src->y += ((y_offset / dest->height) * src->height);
+  src->width *= 1 - (x_clip / dest->width);
+  src->height *= 1 - (y_clip / dest->height);
+
+  dest->x += x_offset;
+  dest->y += y_offset;
+  dest->width -= x_clip;
+  dest->height -= y_clip;
 }
 
-void render_texture_asset(AssetID id, float x, float y, float w, float h) {
+RenderRect get_texture_asset_rect(AssetID id) {
+  RenderRect rect = {0.0f, 0.0f, 0.0f, 0.0f};
+
+  SDL_Texture *texture = get_texture(GameEngine.asset_manager, id);
+
+  if (texture) {
+    int32_t w = 0;
+    int32_t h = 0;
+    if (SDL_QueryTexture(texture, NULL, NULL, &w, &h) == 0) {
+      rect.width = w;
+      rect.height = h;
+    }
+  }
+
+  return rect;
+}
+
+void render_texture_asset(AssetID id, RenderRect *src, RenderRect *dest) {
   if (id < 0) {
     return;
   }
@@ -264,7 +299,7 @@ void render_texture_asset(AssetID id, float x, float y, float w, float h) {
     return;
   }
 
-  render_texture(GameEngine.window.renderer, texture, x, y, w, h);
+  render_texture(GameEngine.window.renderer, texture, src, dest);
 }
 
 void render_text_with_font_asset(AssetID id, const char *text, float x,
@@ -286,7 +321,9 @@ void render_text_with_font_asset(AssetID id, const char *text, float x,
   int32_t h = 0;
   TTF_SizeText(font, text, &w, &h);
 
-  render_surface(GameEngine.window.renderer, surface, x, y, w, h);
+  RenderRect rect = {x, y, w, h};
+
+  render_surface(GameEngine.window.renderer, surface, &rect);
 
   SDL_FreeSurface(surface);
   surface = NULL;