UI DPI scaling:

Recoded the (2.65.1 version) region scale, which happened on loading files with 
different saved size windows. Also scaling window itself was affected.

Old method: scaled region widths based on area/editor scaling factors.
That was leading to too small or too large button regions easily.

New method: region width/height now are in DPI control. Much nicer!
- On changing dpi, buttons remain visually same widths.
- On changing window sizes, the button views and zooms stick to exactly same.

Caveat: people who were using Blender with 'extreme' dpi setting, might find
the layouts slightly differ. Not sure if this is worth version patching...

Todo: overlapping regions that overlap together draw badly. Fix underway.

3 files changed, 15 insertions, 30 deletions

diff --git a/source/blender/editors/screen/area.c b/source/blender/editors/screen/area.c
index cde94ec46ee..b681416250e 100644
--- a/source/blender/editors/screen/area.c
+++ b/source/blender/editors/screen/area.c
@@ -943,8 +943,9 @@ static void region_rect_recursive(wmWindow *win, ScrArea *sa, ARegion *ar, rcti
 	if (ar->next == NULL && alignment != RGN_ALIGN_QSPLIT)
 		alignment = RGN_ALIGN_NONE;
 	
-	/* prefsize, for header we stick to exception */
-	prefsizex = ar->sizex > 1 ? ar->sizex : UI_DPI_FAC * ar->type->prefsizex;
+	/* prefsize, for header we stick to exception (prevent dpi rounding error) */
+	prefsizex = UI_DPI_FAC * (ar->sizex > 1 ? ar->sizex + 0.5f : ar->type->prefsizex);
+	
 	if (ar->regiontype == RGN_TYPE_HEADER) {
 		prefsizey = ED_area_headersize();
 	}
@@ -952,7 +953,7 @@ static void region_rect_recursive(wmWindow *win, ScrArea *sa, ARegion *ar, rcti
 		prefsizey = UI_UNIT_Y * 2 + (UI_UNIT_Y / 2);
 	}
 	else {
-		prefsizey = ar->sizey > 1 ? ar->sizey : UI_DPI_FAC * ar->type->prefsizey;
+		prefsizey = UI_DPI_FAC * (ar->sizey > 1 ? ar->sizey + 0.5f : ar->type->prefsizey);
 	}
 
 
@@ -1092,8 +1093,9 @@ static void region_rect_recursive(wmWindow *win, ScrArea *sa, ARegion *ar, rcti
 	ar->winy = BLI_rcti_size_y(&ar->winrct) + 1;
 	
 	/* if region opened normally, we store this for hide/reveal usage */
-	if (ar->winx > 1) ar->sizex = ar->winx;
-	if (ar->winy > 1) ar->sizey = ar->winy;
+	/* prevent rounding errors for UI_DPI_FAC mult and divide */
+	if (ar->winx > 1) ar->sizex = (ar->winx + 0.5f) /  UI_DPI_FAC;
+	if (ar->winy > 1) ar->sizey = (ar->winy + 0.5f) /  UI_DPI_FAC;
 		
 	/* exception for multiple aligned overlapping regions on same spot */
 	if (ar->overlap)
diff --git a/source/blender/editors/screen/screen_edit.c b/source/blender/editors/screen/screen_edit.c
index f71d63e5fef..c827d8c686b 100644
--- a/source/blender/editors/screen/screen_edit.c
+++ b/source/blender/editors/screen/screen_edit.c
@@ -672,30 +672,7 @@ static void screen_test_scale(bScreen *sc, int winsizex, int winsizey)
 
 			CLAMP(sv->vec.y, 0, winsizey);
 		}
-		
-		/* scale prefsizes of regions */
-		for (sa = sc->areabase.first; sa; sa = sa->next) {
-			ARegion *ar;
-			
-			for (ar = sa->regionbase.first; ar; ar = ar->next) {
-				ar->sizex = (int)((float)ar->sizex * facx);
-				ar->sizey = (int)((float)ar->sizey * facy);
-				ar->winx = (int)((float)ar->winx * facx);
-				ar->winy = (int)((float)ar->winy * facy);
-			}
-			if (sa->spacedata.first) {
-				SpaceLink *sl = sa->spacedata.first;
-				for (sl = sl->next; sl; sl = sl->next) {
-					for (ar = sl->regionbase.first; ar; ar = ar->next) {
-						ar->sizex = (int)((float)ar->sizex * facx);
-						ar->sizey = (int)((float)ar->sizey * facy);
-						ar->winx = (int)((float)ar->winx * facx);
-						ar->winy = (int)((float)ar->winy * facy);
-					}
-				}
-			}
-		}
-	}
+}
 	
 	/* test for collapsed areas. This could happen in some blender version... */
 	/* ton: removed option now, it needs Context... */
diff --git a/source/blender/editors/screen/screen_ops.c b/source/blender/editors/screen/screen_ops.c
index a26f5e87090..a22faea9eec 100644
--- a/source/blender/editors/screen/screen_ops.c
+++ b/source/blender/editors/screen/screen_ops.c
@@ -1759,7 +1759,7 @@ static int region_scale_get_maxsize(RegionMoveData *rmd)
 	int maxsize = 0;
 
 	if (rmd->edge == AE_LEFT_TO_TOPRIGHT || rmd->edge == AE_RIGHT_TO_TOPLEFT) {
-		return rmd->sa->winx - UI_UNIT_X;
+		return  (int) ( (rmd->sa->winx / UI_DPI_FAC) - UI_UNIT_X);
 	}
 
 	if (rmd->ar->regiontype == RGN_TYPE_TOOL_PROPS) {
@@ -1808,6 +1808,9 @@ static int region_scale_modal(bContext *C, wmOperator *op, wmEvent *event)
 				delta = event->x - rmd->origx;
 				if (rmd->edge == AE_LEFT_TO_TOPRIGHT) delta = -delta;
 				
+				/* region sizes now get multiplied */
+				delta /= UI_DPI_FAC;
+				
 				rmd->ar->sizex = rmd->origval + delta;
 				CLAMP(rmd->ar->sizex, 0, rmd->maxsize);
 				
@@ -1824,6 +1827,9 @@ static int region_scale_modal(bContext *C, wmOperator *op, wmEvent *event)
 				delta = event->y - rmd->origy;
 				if (rmd->edge == AE_BOTTOM_TO_TOPLEFT) delta = -delta;
 				
+				/* region sizes now get multiplied */
+				delta /= UI_DPI_FAC;
+
 				rmd->ar->sizey = rmd->origval + delta;
 				CLAMP(rmd->ar->sizey, 0, rmd->maxsize);