Add eyedropper for selecting object & obdata

In addition to the unlink icon to clear a value,
When cleared, show an eyedropper to select objects or object-data
(was already available via the EKey).

source/blender/editors/interface/interface.c

@@ -37,6 +37,7 @@
 
 #include "MEM_guardedalloc.h"
 
+#include "DNA_object_types.h"
 #include "DNA_scene_types.h"
 #include "DNA_screen_types.h"
 #include "DNA_userdef_types.h"
@@ -1951,6 +1952,45 @@ uiBut *ui_but_drag_multi_edit_get(uiBut *but)
 	return but_iter;
 }
 
+/** \name Check to show extra icons
+ *
+ * Extra icons are shown on the right hand side of buttons.
+ * \{ */
+
+static bool ui_but_icon_extra_is_visible_search_unlink(const uiBut *but)
+{
+	BLI_assert(but->type == UI_BTYPE_SEARCH_MENU);
+	return ((but->editstr == NULL) &&
+	        (but->drawstr[0] != '\0') &&
+	        (but->flag & UI_BUT_SEARCH_UNLINK));
+}
+
+static bool ui_but_icon_extra_is_visible_eyedropper(uiBut *but)
+{
+	StructRNA *type = RNA_property_pointer_type(&but->rnapoin, but->rnaprop);
+	const short idcode = RNA_type_to_ID_code(type);
+
+	BLI_assert(but->type == UI_BTYPE_SEARCH_MENU && (but->flag & UI_BUT_SEARCH_UNLINK));
+
+	return ((but->editstr == NULL) &&
+	        (idcode == ID_OB || OB_DATA_SUPPORT_ID(idcode)));
+}
+
+uiButExtraIconType ui_but_icon_extra_get(uiBut *but)
+{
+	if (ui_but_icon_extra_is_visible_search_unlink(but)) {
+		return UI_BUT_ICONEXTRA_UNLINK;
+	}
+	else if (ui_but_icon_extra_is_visible_eyedropper(but)) {
+		return UI_BUT_ICONEXTRA_EYEDROPPER;
+	}
+
+	return UI_BUT_ICONEXTRA_NONE;
+}
+
+/** \} */
+
+
 static double ui_get_but_scale_unit(uiBut *but, double value)
 {
 	UnitSettings *unit = but->block->unit;

source/blender/editors/interface/interface_eyedropper.c

@@ -456,6 +456,8 @@ static void datadropper_exit(bContext *C, wmOperator *op)
 
 		op->customdata = NULL;
 	}
+
+	WM_event_add_mousemove(C);
 }
 
 static void datadropper_cancel(bContext *C, wmOperator *op)

source/blender/editors/interface/interface_handlers.c

@@ -3301,9 +3301,11 @@ static int ui_do_but_TEX(bContext *C, uiBlock *block, uiBut *but, uiHandleButton
 
 static int ui_do_but_SEARCH_UNLINK(bContext *C, uiBlock *block, uiBut *but, uiHandleButtonData *data, const wmEvent *event)
 {
+	uiButExtraIconType extra_icon_type;
+
 	/* unlink icon is on right */
-	if (ELEM(event->type, LEFTMOUSE, EVT_BUT_OPEN, PADENTER, RETKEY) && event->val == KM_PRESS &&
-	    ui_but_is_search_unlink_visible(but))
+	if ((ELEM(event->type, LEFTMOUSE, EVT_BUT_OPEN, PADENTER, RETKEY)) &&
+	    ((extra_icon_type = ui_but_icon_extra_get(but)) != UI_BUT_ICONEXTRA_NONE))
 	{
 		ARegion *ar = data->region;
 		rcti rect;
@@ -3314,14 +3316,29 @@ static int ui_do_but_SEARCH_UNLINK(bContext *C, uiBlock *block, uiBut *but, uiHa
 		BLI_rcti_rctf_copy(&rect, &but->rect);
 		
 		rect.xmin = rect.xmax - (BLI_rcti_size_y(&rect));
+		/* handle click on unlink/eyedropper icon */
 		if (BLI_rcti_isect_pt(&rect, x, y)) {
-			/* most likely NULL, but let's check, and give it temp zero string */
-			if (data->str == NULL)
-				data->str = MEM_callocN(1, "temp str");
-			data->str[0] = 0;
+			/* doing this on KM_PRESS calls eyedropper after clicking unlink icon */
+			if (event->val == KM_RELEASE) {
+				/* unlink */
+				if (extra_icon_type == UI_BUT_ICONEXTRA_UNLINK) {
+					/* most likely NULL, but let's check, and give it temp zero string */
+					if (data->str == NULL) {
+						data->str = MEM_callocN(1, "temp str");
+					}
+					data->str[0] = 0;
 
-			ui_apply_but_TEX(C, but, data);
-			button_activate_state(C, but, BUTTON_STATE_EXIT);
+					ui_apply_but_TEX(C, but, data);
+					button_activate_state(C, but, BUTTON_STATE_EXIT);
+				}
+				/* eyedropper */
+				else if (extra_icon_type == UI_BUT_ICONEXTRA_EYEDROPPER) {
+					WM_operator_name_call(C, "UI_OT_eyedropper_id", WM_OP_INVOKE_DEFAULT, NULL);
+				}
+				else {
+					BLI_assert(0);
+				}
+			}
 
 			return WM_UI_HANDLER_BREAK;
 		}
@@ -6861,14 +6878,6 @@ static bool ui_but_is_interactive(const uiBut *but, const bool labeledit)
 	return true;
 }
 
-bool ui_but_is_search_unlink_visible(const uiBut *but)
-{
-	BLI_assert(but->type == UI_BTYPE_SEARCH_MENU);
-	return ((but->editstr == NULL) &&
-	        (but->drawstr[0] != '\0') &&
-	        (but->flag & UI_BUT_SEARCH_UNLINK));
-}
-
 /* x and y are only used in case event is NULL... */
 static uiBut *ui_but_find_mouse_over_ex(ARegion *ar, const int x, const int y, const bool labeledit)
 {

source/blender/editors/interface/interface_intern.h

@@ -121,6 +121,14 @@ enum {
 	/* warn: rest of uiBut->flag in UI_interface.h */
 };
 
+/* some buttons display icons only under special conditions
+ * (e.g. 'x' icon in search menu) - used with ui_but_icon_extra_get */
+typedef enum uiButExtraIconType {
+	UI_BUT_ICONEXTRA_NONE = 1,
+	UI_BUT_ICONEXTRA_UNLINK,
+	UI_BUT_ICONEXTRA_EYEDROPPER,
+} uiButExtraIconType;
+
 /* but->pie_dir */
 typedef enum RadialDirection {
 	UI_RADIAL_NONE  = -1,
@@ -456,6 +464,7 @@ extern bool ui_but_string_set(struct bContext *C, uiBut *but, const char *str) A
 extern bool ui_but_string_set_eval_num(struct bContext *C, uiBut *but, const char *str, double *value) ATTR_NONNULL();
 extern int  ui_but_string_get_max_length(uiBut *but);
 extern uiBut *ui_but_drag_multi_edit_get(uiBut *but);
+extern uiButExtraIconType ui_but_icon_extra_get(uiBut *but);
 
 extern void ui_but_default_set(struct bContext *C, const bool all, const bool use_afterfunc);
 
@@ -466,7 +475,6 @@ extern bool ui_but_is_unit(const uiBut *but) ATTR_WARN_UNUSED_RESULT;
 extern bool ui_but_is_compatible(const uiBut *but_a, const uiBut *but_b) ATTR_WARN_UNUSED_RESULT;
 extern bool ui_but_is_rna_valid(uiBut *but) ATTR_WARN_UNUSED_RESULT;
 extern bool ui_but_is_utf8(const uiBut *but) ATTR_WARN_UNUSED_RESULT;
-extern bool ui_but_is_search_unlink_visible(const uiBut *but) ATTR_WARN_UNUSED_RESULT;
 
 extern int  ui_but_is_pushed_ex(uiBut *but, double *value) ATTR_WARN_UNUSED_RESULT;
 extern int  ui_but_is_pushed(uiBut *but) ATTR_WARN_UNUSED_RESULT;

source/blender/editors/interface/interface_widgets.c

@@ -1501,6 +1501,7 @@ static void widget_draw_text_icon(uiFontStyle *fstyle, uiWidgetColors *wcol, uiB
 	const bool show_menu_icon = ui_but_draw_menu_icon(but);
 	float alpha = (float)wcol->text[3] / 255.0f;
 	char password_str[UI_MAX_DRAW_STR];
+	uiButExtraIconType extra_icon_type;
 
 	ui_but_text_password_hide(password_str, but, false);
 
@@ -1540,11 +1541,23 @@ static void widget_draw_text_icon(uiFontStyle *fstyle, uiWidgetColors *wcol, uiB
 	}
 
 	/* unlink icon for this button type */
-	if ((but->type == UI_BTYPE_SEARCH_MENU) && ui_but_is_search_unlink_visible(but)) {
+	if ((but->type == UI_BTYPE_SEARCH_MENU) &&
+	    ((extra_icon_type = ui_but_icon_extra_get(but)) != UI_BUT_ICONEXTRA_NONE))
+	{
 		rcti temp = *rect;
 
 		temp.xmin = temp.xmax - (BLI_rcti_size_y(rect) * 1.08f);
-		widget_draw_icon(but, ICON_X, alpha, &temp, false);
+
+		if (extra_icon_type == UI_BUT_ICONEXTRA_UNLINK) {
+			widget_draw_icon(but, ICON_X, alpha, &temp, false);
+		}
+		else if (extra_icon_type == UI_BUT_ICONEXTRA_EYEDROPPER) {
+			widget_draw_icon(but, ICON_EYEDROPPER, alpha, &temp, false);
+		}
+		else {
+			BLI_assert(0);
+		}
+
 		rect->xmax -= ICON_SIZE_FROM_BUTRECT(rect);
 	}