Added line clipping

libsdl-org · Dec 23, 2008 · 4f8e2f5 · 4f8e2f5
1 parent c93a087
commit 4f8e2f5
Show file tree

Hide file tree

Showing 5 changed files with 91 additions and 17 deletions.
diff --git a/include/SDL_rect.h b/include/SDL_rect.h
@@ -104,6 +104,18 @@ extern DECLSPEC void SDLCALL SDL_UnionRect(const SDL_Rect * A,
                                            const SDL_Rect * B,
                                            SDL_Rect * result);
 
+/**
+ * \fn SDL_bool SDL_IntersectRectAndLine(const SDL_Rect *rect, int *X1, int *Y1, int *X2, int *Y2)
+ *
+ * \brief Calculate the intersection of a rectangle and line segment.
+ *
+ * \return SDL_TRUE if there is an intersection, SDL_FALSE otherwise.
+ */
+extern DECLSPEC SDL_bool SDLCALL SDL_IntersectRectAndLine(const SDL_Rect *
+                                                          rect, int *X1,
+                                                          int *Y1, int *X2,
+                                                          int *Y2);
+
 /* Ends C function definitions when using C++ */
 #ifdef __cplusplus
 /* *INDENT-OFF* */

diff --git a/src/video/SDL_blendline.c b/src/video/SDL_blendline.c
@@ -204,11 +204,10 @@ SDL_BlendLine(SDL_Surface * dst, int x1, int y1, int x2, int y2,
     }
 
     /* Perform clipping */
-    /* FIXME
-       if (!SDL_IntersectRect(dstrect, &dst->clip_rect, dstrect)) {
-       return (0);
-       }
-     */
+    if (!SDL_IntersectRectAndLine(&dst->clip_rect, &x1, &x2, &y1, &y2)) {
+        return (0);
+    }
+
 
     if ((blendMode == SDL_BLENDMODE_BLEND)
         || (blendMode == SDL_BLENDMODE_ADD)) {

diff --git a/src/video/SDL_drawline.c b/src/video/SDL_drawline.c
@@ -34,11 +34,9 @@ SDL_DrawLine(SDL_Surface * dst, int x1, int y1, int x2, int y2, Uint32 color)
     }
 
     /* Perform clipping */
-    /* FIXME
-       if (!SDL_IntersectRect(dstrect, &dst->clip_rect, dstrect)) {
-       return (0);
-       }
-     */
+    if (!SDL_IntersectRectAndLine(&dst->clip_rect, &x1, &x2, &y1, &y2)) {
+        return (0);
+    }
 
     switch (dst->format->BytesPerPixel) {
     case 1:

diff --git a/src/video/SDL_rect.c b/src/video/SDL_rect.c
@@ -118,6 +118,75 @@ SDL_UnionRect(const SDL_Rect * A, const SDL_Rect * B, SDL_Rect * result)
     result->h = Amax - Amin;
 }
 
+SDL_bool
+SDL_IntersectRectAndLine(const SDL_Rect *rect, int *X1, int *Y1, int *X2, int *Y2)
+{
+    int x1, y1;
+    int x2, y2;
+    int rectx1;
+    int recty1;
+    int rectx2;
+    int recty2;
+
+    if (!rect || !X1 || !Y1 || !X2 || !Y2) {
+        SDL_FALSE;
+    }
+
+    x1 = *X1;
+    y1 = *Y1;
+    x2 = *X2;
+    y2 = *Y2;
+    rectx1 = rect->x;
+    recty1 = rect->y;
+    rectx2 = rect->x + rect->w - 1;
+    recty2 = rect->y + rect->h - 1;
+
+    /* Check to see if entire line is inside rect */
+    if (x1 >= rectx1 && x1 <= rectx2 && x2 >= rectx1 && x2 <= rectx2 &&
+        y1 >= recty1 && y1 <= recty2 && y2 >= recty1 && y2 <= recty2) {
+        return SDL_TRUE;
+    }
+
+    /* Check to see if entire line is outside rect */
+    if ((x1 < rectx1 && x2 < rectx1) || (x1 > rectx2 && x2 > rectx2) ||
+        (y1 < recty1 && y2 < recty2) || (y1 > recty2 && y2 > recty2)) {
+        return SDL_FALSE;
+    }
+
+    if (y1 = y2) {
+        /* Horizontal line, easy to clip */
+        if (x1 < rectx1) {
+            *X1 = rectx1;
+        } else if (x1 > rectx2) {
+            *X1 = rectx2;
+        }
+        if (x2 < rectx1) {
+            *X2 = rectx1;
+        } else if (x2 > rectx2) {
+            *X2 = rectx2;
+        }
+        return SDL_TRUE;
+    }
+
+    if (x1 == x2) {
+        /* Vertical line, easy to clip */
+        if (y1 < recty1) {
+            *Y1 = recty1;
+        } else if (y1 > recty2) {
+            *Y1 = recty2;
+        }
+        if (y2 < recty1) {
+            *Y2 = recty1;
+        } else if (y2 > recty2) {
+            *Y2 = recty2;
+        }
+        return SDL_TRUE;
+    }
+
+    /* FIXME: need code to clip diagonal line to rect */
+    return SDL_FALSE;
+}
+
 void
 SDL_AddDirtyRect(SDL_DirtyRectList * list, const SDL_Rect * rect)
 {

diff --git a/src/video/SDL_video.c b/src/video/SDL_video.c
@@ -2119,19 +2119,15 @@ SDL_RenderLine(int x1, int y1, int x2, int y2)
         SDL_Unsupported();
         return -1;
     }
-#if 0
-    //FIXME: Need line intersect routine
     window = SDL_GetWindowFromID(renderer->window);
+
     real_rect.x = 0;
     real_rect.y = 0;
     real_rect.w = window->w;
     real_rect.h = window->h;
-    if (rect) {
-        if (!SDL_IntersectRect(rect, &real_rect, &real_rect)) {
-            return 0;
-        }
+    if (!SDL_IntersectRectAndLine(&real_rect, &x1, &x2, &y1, &y2)) {
+        return (0);
     }
-#endif
     return renderer->RenderLine(renderer, x1, y1, x2, y2);
 }