UI: preset popover buttons in panel headers.

Moves the preset into a menu for the panel header, so it can be changed
without opening the panel and takes up less space. Two remaining issues:

* For long lists the add new preset button can be scrolled off screen.
* We should support showing the name of the chosen preset in the panel
  header, but the current preset system does not support detecting which
  preset is used.

Differential Revision: https://developer.blender.org/D3366

5 files changed, 53 insertions, 7 deletions

diff --git a/source/blender/blenkernel/BKE_screen.h b/source/blender/blenkernel/BKE_screen.h
index 4270e6eb1b4..1b42ce97940 100644
--- a/source/blender/blenkernel/BKE_screen.h
+++ b/source/blender/blenkernel/BKE_screen.h
@@ -216,6 +216,8 @@ typedef struct PanelType {
 	int (*poll)(const struct bContext *C, struct PanelType *pt);
 	/* draw header (optional) */
 	void (*draw_header)(const struct bContext *C, struct Panel *pa);
+	/* draw header preset (optional) */
+	void (*draw_header_preset)(const struct bContext *C, struct Panel *pa);
 	/* draw entirely, view changes should be handled here */
 	void (*draw)(const struct bContext *C, struct Panel *pa);
 
diff --git a/source/blender/editors/include/UI_icons.h b/source/blender/editors/include/UI_icons.h
index 3bc1255d23f..659f6c97696 100644
--- a/source/blender/editors/include/UI_icons.h
+++ b/source/blender/editors/include/UI_icons.h
@@ -113,9 +113,7 @@ DEF_ICON(FILE_TICK)
 DEF_ICON(QUIT)
 DEF_ICON(URL)
 DEF_ICON(RECOVER_LAST)
-#ifndef DEF_ICON_BLANK_SKIP
-	DEF_ICON(BLANK038)
-#endif
+DEF_ICON(PRESET)
 DEF_ICON(FULLSCREEN_ENTER)
 DEF_ICON(FULLSCREEN_EXIT)
 DEF_ICON(BLANK1)	// Not actually blank - this is used all over the place
diff --git a/source/blender/editors/interface/interface_region_popover.c b/source/blender/editors/interface/interface_region_popover.c
index e769d367b45..fb14ca745c6 100644
--- a/source/blender/editors/interface/interface_region_popover.c
+++ b/source/blender/editors/interface/interface_region_popover.c
@@ -168,11 +168,17 @@ static uiBlock *ui_block_func_POPOVER(bContext *C, uiPopupBlockHandle *handle, v
 			block->my = handle->prev_my;
 		}
 
-		/* Prefer popover from header to be positioned into the editor. */
 		if (!slideout) {
 			ScrArea *sa = CTX_wm_area(C);
-			if (sa && ED_area_header_alignment(sa) == RGN_ALIGN_BOTTOM) {
-				ARegion *ar = CTX_wm_region(C);
+			ARegion *ar = CTX_wm_region(C);
+
+			if (ar && ar->panels.first) {
+				/* For regions with panels, prefer to open to top so we can
+				 * see the values of the buttons below changing. */
+				UI_block_direction_set(block, UI_DIR_UP | UI_DIR_CENTER_X);
+			}
+			else if (sa && ED_area_header_alignment(sa) == RGN_ALIGN_BOTTOM) {
+				/* Prefer popover from header to be positioned into the editor. */
 				if (ar && ar->regiontype == RGN_TYPE_HEADER) {
 					UI_block_direction_set(block, UI_DIR_UP | UI_DIR_CENTER_X);
 				}
diff --git a/source/blender/editors/screen/area.c b/source/blender/editors/screen/area.c
index 478afa64939..02ce64bc915 100644
--- a/source/blender/editors/screen/area.c
+++ b/source/blender/editors/screen/area.c
@@ -1861,6 +1861,21 @@ static void ed_panel_draw(const bContext *C,
 	/* bad fixed values */
 	int xco, yco, h = 0;
 
+	if (pt->draw_header_preset && !(pt->flag & PNL_NO_HEADER) && (open || vertical)) {
+		/* for preset menu */
+		panel->layout = UI_block_layout(
+		        block, UI_LAYOUT_HORIZONTAL, UI_LAYOUT_HEADER,
+		        0, (UI_UNIT_Y * 1.1f) + style->panelspace, UI_UNIT_Y, 1, 0, style);
+
+		pt->draw_header_preset(C, panel);
+
+		int headerend = w - UI_UNIT_X;
+
+		UI_block_layout_resolve(block, &xco, &yco);
+		UI_block_translate(block, headerend - xco, 0);
+		panel->layout = NULL;
+	}
+
 	if (pt->draw_header && !(pt->flag & PNL_NO_HEADER) && (open || vertical)) {
 		int labelx, labely;
 		UI_panel_label_offset(block, &labelx, &labely);
diff --git a/source/blender/makesrna/intern/rna_ui.c b/source/blender/makesrna/intern/rna_ui.c
index ebee502515f..8083ae35dc1 100644
--- a/source/blender/makesrna/intern/rna_ui.c
+++ b/source/blender/makesrna/intern/rna_ui.c
@@ -166,6 +166,24 @@ static void panel_draw_header(const bContext *C, Panel *pnl)
 	RNA_parameter_list_free(&list);
 }
 
+static void panel_draw_header_preset(const bContext *C, Panel *pnl)
+{
+	extern FunctionRNA rna_Panel_draw_header_preset_func;
+
+	PointerRNA ptr;
+	ParameterList list;
+	FunctionRNA *func;
+
+	RNA_pointer_create(&CTX_wm_screen(C)->id, pnl->type->ext.srna, pnl, &ptr);
+	func = &rna_Panel_draw_header_preset_func;
+
+	RNA_parameter_list_create(&list, &ptr, func);
+	RNA_parameter_set_lookup(&list, "context", &C);
+	pnl->type->ext.call((bContext *)C, &ptr, func, &list);
+
+	RNA_parameter_list_free(&list);
+}
+
 static void rna_Panel_unregister(Main *UNUSED(bmain), StructRNA *type)
 {
 	ARegionType *art;
@@ -199,7 +217,7 @@ static StructRNA *rna_Panel_register(
 	PanelType *pt, *parent = NULL, dummypt = {NULL};
 	Panel dummypanel = {NULL};
 	PointerRNA dummyptr;
-	int have_function[3];
+	int have_function[4];
 
 	/* setup dummy panel & panel type to store static properties in */
 	dummypanel.type = &dummypt;
@@ -267,6 +285,7 @@ static StructRNA *rna_Panel_register(
 	pt->poll = (have_function[0]) ? panel_poll : NULL;
 	pt->draw = (have_function[1]) ? panel_draw : NULL;
 	pt->draw_header = (have_function[2]) ? panel_draw_header : NULL;
+	pt->draw_header_preset = (have_function[3]) ? panel_draw_header_preset : NULL;
 
 	/* XXX use "no header" flag for some ordering of panels until we have real panel ordering */
 	if (pt->flag & PNL_NO_HEADER) {
@@ -1058,6 +1077,12 @@ static void rna_def_panel(BlenderRNA *brna)
 	parm = RNA_def_pointer(func, "context", "Context", "", "");
 	RNA_def_parameter_flags(parm, PROP_NEVER_NULL, PARM_REQUIRED);
 
+	func = RNA_def_function(srna, "draw_header_preset", NULL);
+	RNA_def_function_ui_description(func, "Draw UI elements for presets in the panel's header");
+	RNA_def_function_flag(func, FUNC_REGISTER_OPTIONAL);
+	parm = RNA_def_pointer(func, "context", "Context", "", "");
+	RNA_def_parameter_flags(parm, PROP_NEVER_NULL, PARM_REQUIRED);
+
 	prop = RNA_def_property(srna, "layout", PROP_POINTER, PROP_NONE);
 	RNA_def_property_struct_type(prop, "UILayout");
 	RNA_def_property_ui_text(prop, "Layout", "Defines the structure of the panel in the UI");