First attempt at optimising the redraw of frame scrolls. some of these calculations are wrong.

5 files changed, 100 insertions, 4 deletions

diff --git a/desktop/browser.c b/desktop/browser.c
index 89484609e..0ecb0ac77 100644
--- a/desktop/browser.c
+++ b/desktop/browser.c
@@ -1947,6 +1947,38 @@ void browser_window_update_box(struct browser_window *bw, struct rect *rect)
 }
 
 
+/* exported interface, documented in browser.h */
+void browser_window_copy_box(struct browser_window *bw, struct rect *rect, int x, int y)
+{
+	int pos_x;
+	int pos_y;
+	struct browser_window *top;
+
+	assert(bw);
+
+	if (bw->window != NULL) {
+		/* Front end window */
+		if(gui_window_copy_box(bw->window, rect, x, y) == false) {
+			gui_window_update_box(bw->window, rect);
+		}
+	} else {
+		/* Core managed browser window */
+		browser_window_get_position(bw, true, &pos_x, &pos_y);
+
+		top = browser_window_get_root(bw);
+
+		rect->x0 += pos_x / bw->scale;
+		rect->y0 += pos_y / bw->scale;
+		rect->x1 += pos_x / bw->scale;
+		rect->y1 += pos_y / bw->scale;
+
+		if(gui_window_copy_box(top->window, rect, x + pos_x, y + pos_y) == false) {
+			gui_window_update_box(top->window, rect);
+		}
+	}
+}
+
+
 /**
  * Stop all fetching activity in a browser window.
  *
diff --git a/desktop/browser.h b/desktop/browser.h
index f3c68fa09..b0965e1c3 100644
--- a/desktop/browser.h
+++ b/desktop/browser.h
@@ -95,6 +95,17 @@ void browser_window_set_scale(struct browser_window *bw, float scale, bool all);
 float browser_window_get_scale(struct browser_window *bw);
 
 /**
+ * Copy an area of the browser window to the given x,y co-ordinates.
+ * Source and destination may overlap.
+ *
+ * \param bw	browser window
+ * \param rect	area to copy
+ * \param x	x-coordinate of destination to copy to
+ * \param y	y-coordinate of destination to copy to
+ */
+void browser_window_copy_box(struct browser_window *bw, struct rect *rect, int x, int y);
+
+/**
  * Get access to any content, link URLs and objects (images) currently
  * at the given (x, y) coordinates.
  *
diff --git a/desktop/browser_private.h b/desktop/browser_private.h
index 91372acc3..d008d887a 100644
--- a/desktop/browser_private.h
+++ b/desktop/browser_private.h
@@ -110,6 +110,10 @@ struct browser_window {
 
 	struct scrollbar *scroll_x;  /**< Horizontal scroll. */
 	struct scrollbar *scroll_y;  /**< Vertical scroll. */
+	
+	/** previous scroll offsets */
+	int prev_scroll_x;
+	int prev_scroll_y;
 
 	/** scale of window contents */
 	float scale;
diff --git a/desktop/frames.c b/desktop/frames.c
index cc2cabfd2..4de33cb4f 100644
--- a/desktop/frames.c
+++ b/desktop/frames.c
@@ -64,13 +64,49 @@ void browser_window_scroll_callback(void *client_data,
 			html_redraw_a_box(bw->parent->current_content, bw->box);
 		} else {
 			struct rect rect;
+			struct rect copyrect;
+			int dest_x = 0;
+			int dest_y = 0;
+			int cur_x = scrollbar_get_offset(bw->scroll_x);
+			int cur_y = scrollbar_get_offset(bw->scroll_y);
+			
+			if(cur_x > bw->prev_scroll_x) {
+				copyrect.x0 = cur_x;
+				copyrect.x1 = copyrect.x0 + bw->width - (cur_x - bw->prev_scroll_x);
+				dest_x = bw->prev_scroll_x;
+
+				rect.x0 = copyrect.x0;				
+				rect.x1 = copyrect.x0 + bw->width - (cur_x - bw->prev_scroll_x);
+			} else {
+				copyrect.x0 = bw->prev_scroll_x;
+				copyrect.x1 = copyrect.x0 + bw->width - (bw->prev_scroll_x - cur_x);
+				dest_x = cur_x;
+				
+				rect.x0 = cur_x;
+				rect.x1 = cur_x + bw->width - (bw->prev_scroll_x - cur_x);
+			}
 
-			rect.x0 = scrollbar_get_offset(bw->scroll_x);
-			rect.y0 = scrollbar_get_offset(bw->scroll_y);
-			rect.x1 = rect.x0 + bw->width;
-			rect.y1 = rect.y0 + bw->height;
+			if(cur_y > bw->prev_scroll_y) {
+				copyrect.y0 = cur_y;
+				copyrect.y1 = copyrect.y0 + bw->height - (cur_y - bw->prev_scroll_y);
+				dest_y = bw->prev_scroll_y;
+				
+				rect.y0 = copyrect.y0;				
+				rect.y1 = copyrect.y0 + bw->height - (cur_y - bw->prev_scroll_y);
+			} else {
+				copyrect.y0 = bw->prev_scroll_y;
+				copyrect.y1 = copyrect.y0 + bw->height - (bw->prev_scroll_y - cur_y);
+				dest_y = cur_y;
+
+				rect.y0 = cur_y;
+				rect.y1 = cur_y + bw->height - (bw->prev_scroll_y - cur_y);
+			}
 
+			browser_window_copy_box(bw, &copyrect, dest_x, dest_y);
 			browser_window_update_box(bw, &rect);
+			
+			bw->prev_scroll_x = scrollbar_get_offset(bw->scroll_x);
+			bw->prev_scroll_y = scrollbar_get_offset(bw->scroll_y);
 		}
 		break;
 	case SCROLLBAR_MSG_SCROLL_START:
diff --git a/desktop/gui.h b/desktop/gui.h
index 48684c3c5..551848586 100644
--- a/desktop/gui.h
+++ b/desktop/gui.h
@@ -79,6 +79,19 @@ void gui_window_set_title(struct gui_window *g, const char *title);
 void gui_window_redraw_window(struct gui_window *g);
 void gui_window_update_box(struct gui_window *g,
 		const struct rect *rect);
+		
+/**
+ * Copy an area of the displayed gui_window to the co-ordinates
+ * specified by x,y.  NB: source and destination may overlap.
+ *
+ * \param g The window to perform the copy on.
+ * \param rect The rectangle to copy.
+ * \param x The X co-ordinate to copy to.
+ * \param y The Y co-ordinate to copy to.
+ * \return true if the region could be copied, false otherwise.
+ */
+bool gui_window_copy_box(struct gui_window *g, const struct rect *rect, int x, int y);
+
 bool gui_window_get_scroll(struct gui_window *g, int *sx, int *sy);
 void gui_window_set_scroll(struct gui_window *g, int sx, int sy);
 void gui_window_scroll_visible(struct gui_window *g, int x0, int y0,