RISC OS: Fix EX0 EY0 rendering glitches when scrolling.

4 files changed, 42 insertions, 12 deletions

diff --git a/frontends/riscos/corewindow.c b/frontends/riscos/corewindow.c
index 2ef05da29..921671217 100644
--- a/frontends/riscos/corewindow.c
+++ b/frontends/riscos/corewindow.c
@@ -120,10 +120,15 @@ static void ro_cw_redraw(wimp_draw *redraw)
 		origin_x = redraw->box.x0 - redraw->xscroll;
 		origin_y = redraw->box.y1 + ro_cw->origin_y - redraw->yscroll;
 
-		r.x0 = (redraw->clip.x0 - origin_x) / 2;
-		r.y0 = (origin_y - redraw->clip.y1) / 2;
-		r.x1 = r.x0 + ((redraw->clip.x1 - redraw->clip.x0) / 2);
-		r.y1 = r.y0 + ((redraw->clip.y1 - redraw->clip.y0) / 2);
+		ro_plot_clip_rect.x0 = redraw->clip.x0 - origin_x;
+		ro_plot_clip_rect.y0 = origin_y - redraw->clip.y0;
+		ro_plot_clip_rect.x1 = redraw->clip.x1 - origin_x;
+		ro_plot_clip_rect.y1 = origin_y - redraw->clip.y1;
+
+		r.x0 = (ro_plot_clip_rect.x0    ) / 2; /* left   */
+		r.y0 = (ro_plot_clip_rect.y1    ) / 2; /* top    */
+		r.x1 = (ro_plot_clip_rect.x1 + 1) / 2; /* right  */
+		r.y1 = (ro_plot_clip_rect.y0 + 1) / 2; /* bottom */
 
 		/* call the draw callback */
 		ro_cw->draw(ro_cw, origin_x, origin_y, &r);
diff --git a/frontends/riscos/gui.h b/frontends/riscos/gui.h
index 831c57dc7..5ff17e922 100644
--- a/frontends/riscos/gui.h
+++ b/frontends/riscos/gui.h
@@ -165,6 +165,7 @@ void ro_gui_print_prepare(struct gui_window *g);
 extern const struct plotter_table ro_plotters;
 extern int ro_plot_origin_x;
 extern int ro_plot_origin_y;
+extern struct rect ro_plot_clip_rect;
 
 /* in theme_install.c */
 bool ro_gui_theme_install_apply(wimp_w w);
diff --git a/frontends/riscos/plotters.c b/frontends/riscos/plotters.c
index 25c953f97..e38e746cd 100644
--- a/frontends/riscos/plotters.c
+++ b/frontends/riscos/plotters.c
@@ -39,6 +39,7 @@
 
 int ro_plot_origin_x = 0;
 int ro_plot_origin_y = 0;
+struct rect ro_plot_clip_rect;
 
 /** One version of the A9home OS is incapable of drawing patterned lines */
 bool ro_plot_patterned_lines = true;
@@ -115,6 +116,14 @@ ro_plot_clip(const struct redraw_context *ctx, const struct rect *clip)
 	int clip_x1 = clip->x1 * 2;
 	int clip_y1 = clip->y0 * 2;
 
+	/* Avoid artefacts due to clip rectangle offsetting in EX0 EY0 modes.
+	 * The area the WIMP asked us to draw might have dimensions that are
+	 * not a multiple of 2. */
+	if (clip_x0 < ro_plot_clip_rect.x0) clip_x0 = ro_plot_clip_rect.x0;
+	if (clip_x1 > ro_plot_clip_rect.x1) clip_x1 = ro_plot_clip_rect.x1;
+	if (clip_y0 > ro_plot_clip_rect.y0) clip_y0 = ro_plot_clip_rect.y0;
+	if (clip_y1 < ro_plot_clip_rect.y1) clip_y1 = ro_plot_clip_rect.y1;
+
 	clip_x0 = ro_plot_origin_x + clip_x0;
 	clip_y0 = ro_plot_origin_y - clip_y0;
 	clip_x1 = ro_plot_origin_x + clip_x1 - 1;
diff --git a/frontends/riscos/window.c b/frontends/riscos/window.c
index f1728afce..24662365c 100644
--- a/frontends/riscos/window.c
+++ b/frontends/riscos/window.c
@@ -1685,13 +1685,19 @@ static void ro_gui_window_redraw(wimp_draw *redraw)
 		ro_plot_origin_x = redraw->box.x0 - redraw->xscroll;
 		ro_plot_origin_y = redraw->box.y1 - redraw->yscroll;
 
+		/* Adjust clip rect for origin. */
+		ro_plot_clip_rect.x0 = redraw->clip.x0 - ro_plot_origin_x;
+		ro_plot_clip_rect.y0 = ro_plot_origin_y - redraw->clip.y0;
+		ro_plot_clip_rect.x1 = redraw->clip.x1 - ro_plot_origin_x;
+		ro_plot_clip_rect.y1 = ro_plot_origin_y - redraw->clip.y1;
+
 		/* Convert OS redraw rectangle request coordinates into NetSurf
 		 * coordinates. NetSurf coordinates have origin at top left of
 		 * document and units are in px. */
-		clip.x0 = (redraw->clip.x0 - ro_plot_origin_x) / 2; /* left   */
-		clip.y0 = (ro_plot_origin_y - redraw->clip.y1) / 2; /* top    */
-		clip.x1 = (redraw->clip.x1 - ro_plot_origin_x) / 2; /* right  */
-		clip.y1 = (ro_plot_origin_y - redraw->clip.y0) / 2; /* bottom */
+		clip.x0 = (ro_plot_clip_rect.x0    ) / 2; /* left   */
+		clip.y0 = (ro_plot_clip_rect.y1    ) / 2; /* top    */
+		clip.x1 = (ro_plot_clip_rect.x1 + 1) / 2; /* right  */
+		clip.y1 = (ro_plot_clip_rect.y0 + 1) / 2; /* bottom */
 
 		if (ro_gui_current_redraw_gui->option.buffer_everything)
 			ro_gui_buffer_open(redraw);
@@ -4715,10 +4721,19 @@ void ro_gui_window_update_boxes(void)
 		ro_plot_origin_y = update.box.y1 - update.yscroll;
 
 		while (more) {
-			clip.x0 = (update.clip.x0 - ro_plot_origin_x) / 2;
-			clip.y0 = (ro_plot_origin_y - update.clip.y1) / 2;
-			clip.x1 = (update.clip.x1 - ro_plot_origin_x) / 2;
-			clip.y1 = (ro_plot_origin_y - update.clip.y0) / 2;
+			/* Adjust clip rect for origin. */
+			ro_plot_clip_rect.x0 = update.clip.x0 - ro_plot_origin_x;
+			ro_plot_clip_rect.y0 = ro_plot_origin_y - update.clip.y0;
+			ro_plot_clip_rect.x1 = update.clip.x1 - ro_plot_origin_x;
+			ro_plot_clip_rect.y1 = ro_plot_origin_y - update.clip.y1;
+
+			/* Convert OS redraw rectangle request coordinates into
+			 * NetSurf coordinates. NetSurf coordinates have origin
+			 * at top left of document and units are in px. */
+			clip.x0 = (ro_plot_clip_rect.x0    ) / 2; /* left   */
+			clip.y0 = (ro_plot_clip_rect.y1    ) / 2; /* top    */
+			clip.x1 = (ro_plot_clip_rect.x1 + 1) / 2; /* right  */
+			clip.y1 = (ro_plot_clip_rect.y0 + 1) / 2; /* bottom */
 
 			if (use_buffer)
 				ro_gui_buffer_open(&update);