UI: Style drag-drop indicators as tooltips

Currently, the drop indicator colors are hardcoded to white text on semi-transparent black background.
This patch makes the drop indicator use the tooltip theme settings, as they serve a similar purpose.

{F10530482, size=full}

All built-in themes seem to work well and got improved readability.

Reviewed By: HooglyBoogly

Differential Revision: https://developer.blender.org/D12588

source/blender/windowmanager/intern/wm_dragdrop.c

@@ -34,6 +34,7 @@
 #include "BLT_translation.h"
 
 #include "BLI_blenlib.h"
+#include "BLI_math_color.h"
 
 #include "BIF_glutil.h"
 
@@ -50,6 +51,7 @@
 
 #include "UI_interface.h"
 #include "UI_interface_icons.h"
+#include "UI_resources.h"
 
 #include "RNA_access.h"
 
@@ -463,8 +465,14 @@ void WM_drag_free_imported_drag_ID(struct Main *bmain, wmDrag *drag, wmDropBox *
 static void wm_drop_operator_draw(const char *name, int x, int y)
 {
   const uiFontStyle *fstyle = UI_FSTYLE_WIDGET;
-  const float col_fg[4] = {1.0f, 1.0f, 1.0f, 1.0f};
-  const float col_bg[4] = {0.0f, 0.0f, 0.0f, 0.2f};
+
+  /* Use the theme settings from tooltips. */
+  const bTheme *btheme = UI_GetTheme();
+  const uiWidgetColors *wcol = &btheme->tui.wcol_tooltip;
+
+  float col_fg[4], col_bg[4];
+  rgba_uchar_to_float(col_fg, wcol->text);
+  rgba_uchar_to_float(col_bg, wcol->inner);
 
   UI_fontstyle_draw_simple_backdrop(fstyle, x, y, name, col_fg, col_bg);
 }