Fix a number of small errors in area coordinate handling

For example collapsing the lower part of the topbar with 2x interface scale
would hide the top-bar header region. There were also more asserts when changing
window size and moving area edges afterwards (same assert as in T55298).
Fixes are similar to e626998a262ebe4f.

With all the recent fixes I've done, area geometry handling should be stable
again. Let's hope I'm right :)

5 files changed, 50 insertions, 12 deletions

diff --git a/source/blender/editors/include/ED_screen.h b/source/blender/editors/include/ED_screen.h
index 1b5425b54c8..a2a619209db 100644
--- a/source/blender/editors/include/ED_screen.h
+++ b/source/blender/editors/include/ED_screen.h
@@ -150,6 +150,8 @@ void    ED_area_swapspace(struct bContext *C, ScrArea *sa1, ScrArea *sa2);
 int     ED_area_headersize(void);
 int     ED_area_header_alignment(const ScrArea *area);
 int     ED_area_global_size_y(const ScrArea *area);
+int     ED_area_global_min_size_y(const ScrArea *area);
+int     ED_area_global_max_size_y(const ScrArea *area);
 bool    ED_area_is_global(const ScrArea *area);
 int     ED_region_global_size_y(void);
 void    ED_area_update_region_sizes(struct wmWindowManager *wm, struct wmWindow *win, struct ScrArea *area);
diff --git a/source/blender/editors/screen/area.c b/source/blender/editors/screen/area.c
index 16eeff01e58..e96580855d3 100644
--- a/source/blender/editors/screen/area.c
+++ b/source/blender/editors/screen/area.c
@@ -2362,6 +2362,16 @@ int ED_area_global_size_y(const ScrArea *area)
 	BLI_assert(ED_area_is_global(area));
 	return round_fl_to_int(area->global->cur_fixed_height * UI_DPI_FAC);
 }
+int ED_area_global_min_size_y(const ScrArea *area)
+{
+	BLI_assert(ED_area_is_global(area));
+	return round_fl_to_int(area->global->size_min * UI_DPI_FAC);
+}
+int ED_area_global_max_size_y(const ScrArea *area)
+{
+	BLI_assert(ED_area_is_global(area));
+	return round_fl_to_int(area->global->size_max * UI_DPI_FAC);
+}
 
 bool ED_area_is_global(const ScrArea *area)
 {
diff --git a/source/blender/editors/screen/screen_edit.c b/source/blender/editors/screen/screen_edit.c
index c3d18abc2cf..b3424ae3fb4 100644
--- a/source/blender/editors/screen/screen_edit.c
+++ b/source/blender/editors/screen/screen_edit.c
@@ -718,7 +718,7 @@ static void screen_vertices_scale(
 		/* adjust headery if verts are along the edge of window */
 		if (sa->v1->vec.y > window_rect->ymin)
 			headery += U.pixelsize;
-		if (sa->v2->vec.y < window_rect->ymax)
+		if (sa->v2->vec.y < (window_rect->ymax - 1))
 			headery += U.pixelsize;
 
 		if (area_geometry_height(sa) < headery) {
@@ -744,21 +744,32 @@ static void screen_vertices_scale(
 
 	/* Global areas have a fixed size that only changes with the DPI. Here we ensure that exactly this size is set. */
 	for (ScrArea *area = win->global_areas.areabase.first; area; area = area->next) {
+		int height = ED_area_global_size_y(area) - 1;
+
 		if (area->global->flag & GLOBAL_AREA_IS_HIDDEN) {
 			continue;
 		}
+
+		if (area->v1->vec.y > window_rect->ymin) {
+			height += U.pixelsize;
+		}
+		if (area->v2->vec.y < (window_rect->ymax - 1)) {
+			height += U.pixelsize;
+		}
+
 		/* width */
 		area->v1->vec.x = area->v2->vec.x = window_rect->xmin;
 		area->v3->vec.x = area->v4->vec.x = window_rect->xmax - 1;
 		/* height */
 		area->v1->vec.y = area->v4->vec.y = window_rect->ymin;
 		area->v2->vec.y = area->v3->vec.y = window_rect->ymax - 1;
+
 		switch (area->global->align) {
 			case GLOBAL_AREA_ALIGN_TOP:
-				area->v1->vec.y = area->v4->vec.y = area->v2->vec.y - ED_area_global_size_y(area);
+				area->v1->vec.y = area->v4->vec.y = area->v2->vec.y - height;
 				break;
 			case GLOBAL_AREA_ALIGN_BOTTOM:
-				area->v2->vec.y = area->v3->vec.y = area->v1->vec.y + ED_area_global_size_y(area);
+				area->v2->vec.y = area->v3->vec.y = area->v1->vec.y + height;
 				break;
 		}
 	}
diff --git a/source/blender/editors/screen/screen_ops.c b/source/blender/editors/screen/screen_ops.c
index e4de87e0b46..9c27bda5ec8 100644
--- a/source/blender/editors/screen/screen_ops.c
+++ b/source/blender/editors/screen/screen_ops.c
@@ -1235,8 +1235,8 @@ static void area_move_set_limits(
 	if (use_bigger_smaller_snap != NULL) {
 		*use_bigger_smaller_snap = false;
 		for (ScrArea *area = win->global_areas.areabase.first; area; area = area->next) {
-			const int size_min = round_fl_to_int(area->global->size_min * UI_DPI_FAC);
-			const int size_max = round_fl_to_int(area->global->size_max * UI_DPI_FAC);
+			const int size_min = ED_area_global_min_size_y(area) - 1;
+			const int size_max = ED_area_global_max_size_y(area) - 1;
 
 			/* logic here is only tested for lower edge :) */
 			/* left edge */
diff --git a/source/blender/windowmanager/intern/wm_window.c b/source/blender/windowmanager/intern/wm_window.c
index 7ca51724268..43231855162 100644
--- a/source/blender/windowmanager/intern/wm_window.c
+++ b/source/blender/windowmanager/intern/wm_window.c
@@ -2013,22 +2013,37 @@ void WM_window_rect_calc(const wmWindow *win, rcti *r_rect)
  */
 void WM_window_screen_rect_calc(const wmWindow *win, rcti *r_rect)
 {
-	rcti rect;
+	rcti window_rect, screen_rect;
 
-	BLI_rcti_init(&rect, 0, WM_window_pixels_x(win), 0, WM_window_pixels_y(win));
+	WM_window_rect_calc(win, &window_rect);
+	screen_rect = window_rect;
 
 	/* Substract global areas from screen rectangle. */
 	for (ScrArea *global_area = win->global_areas.areabase.first; global_area; global_area = global_area->next) {
+		int height = ED_area_global_size_y(global_area) - 1;
+
 		if (global_area->global->flag & GLOBAL_AREA_IS_HIDDEN) {
 			continue;
 		}
 
 		switch (global_area->global->align) {
 			case GLOBAL_AREA_ALIGN_TOP:
-				rect.ymax -= ED_area_global_size_y(global_area);
+				if ((screen_rect.ymax - height) > window_rect.ymin) {
+					height += U.pixelsize;
+				}
+				if (screen_rect.ymax < (window_rect.ymax - 1)) {
+					height += U.pixelsize;
+				}
+				screen_rect.ymax -= height;
 				break;
 			case GLOBAL_AREA_ALIGN_BOTTOM:
-				rect.ymin += ED_area_global_size_y(global_area);
+				if (screen_rect.ymin > window_rect.ymin) {
+					height += U.pixelsize;
+				}
+				if ((screen_rect.ymin + height) < (window_rect.ymax - 1)) {
+					height += U.pixelsize;
+				}
+				screen_rect.ymin += height;
 				break;
 			default:
 				BLI_assert(0);
@@ -2036,9 +2051,9 @@ void WM_window_screen_rect_calc(const wmWindow *win, rcti *r_rect)
 		}
 	}
 
-	BLI_assert(rect.xmin < rect.xmax);
-	BLI_assert(rect.ymin < rect.ymax);
-	*r_rect = rect;
+	BLI_assert(screen_rect.xmin < screen_rect.xmax);
+	BLI_assert(screen_rect.ymin < screen_rect.ymax);
+	*r_rect = screen_rect;
 }
 
 bool WM_window_is_fullscreen(wmWindow *win)