Expose PreviewImage & custom icons to py API.

This commit mainly:

* Exposes PreviewImage struct in RNA, including ways for user to set images data.
* Adds a new kind of PreviewImage, using a file path and IMB_thumb to get image.
* Adds a new kind of custom icon using PreviewImage, unrelated to ID previews system.
* Adds a python API (utils.previews) to allow python scripts to access those custom previews/icons.

Note that loading image from files' thumbnails is done when needed (deferred loading), not
when defining the custom preview/icon.

WARNING: for release addons who would want to use this, please keep it to a strict minimum, really needed level.
We do not want our UI to explode under hundreds of different flashy icons!

For more info, see also the release notes of Blender 2.75 (http://wiki.blender.org/index.php/Dev:Ref/Release_Notes/2.75/Addons)
and the example/templates featured with Blender.

Patch by Campbell (ideasman42), Inês (brita) and Bastien (mont29).

Differential Revision: https://developer.blender.org/D1255

1 files changed, 22 insertions, 19 deletions

diff --git a/source/blender/editors/interface/interface.c b/source/blender/editors/interface/interface.c
index b63871f5c82..a9cc926b275 100644
--- a/source/blender/editors/interface/interface.c
+++ b/source/blender/editors/interface/interface.c
@@ -3237,6 +3237,18 @@ static uiBut *ui_def_but(
 	return but;
 }
 
+void ui_def_but_icon(uiBut *but, const int icon, const int flag) {
+	if (icon) {
+		ui_icon_ensure_deferred(but->block->evil_C, icon, (flag & UI_BUT_ICON_PREVIEW) != 0);
+	}
+	but->icon = (BIFIconID)icon;
+	but->flag |= flag;
+
+	if (but->str && but->str[0]) {
+		but->drawflag |= UI_BUT_ICON_LEFT;
+	}
+}
+
 static void ui_def_but_rna__disable(uiBut *but)
 {
 	but->flag |= UI_BUT_DISABLED;
@@ -3500,11 +3512,7 @@ static uiBut *ui_def_but_rna(
 		but->rnaindex = 0;
 
 	if (icon) {
-		but->icon = (BIFIconID)icon;
-		but->flag |= UI_HAS_ICON;
-		if (str[0]) {
-			but->drawflag |= UI_BUT_ICON_LEFT;
-		}
+		ui_def_but_icon(but, icon, UI_HAS_ICON);
 	}
 	
 	if ((type == UI_BTYPE_MENU) && (but->dt == UI_EMBOSS_PULLDOWN)) {
@@ -3691,8 +3699,7 @@ int UI_autocomplete_end(AutoComplete *autocpl, char *autoname)
 static void ui_but_update_and_icon_set(uiBut *but, int icon)
 {
 	if (icon) {
-		but->icon = (BIFIconID) icon;
-		but->flag |= UI_HAS_ICON;
+		ui_def_but_icon(but, icon, UI_HAS_ICON);
 	}
 
 	ui_but_update(but);
@@ -4066,7 +4073,7 @@ void UI_but_drag_set_value(uiBut *but)
 void UI_but_drag_set_image(uiBut *but, const char *path, int icon, struct ImBuf *imb, float scale)
 {
 	but->dragtype = WM_DRAG_PATH;
-	but->icon = icon; /* no flag UI_HAS_ICON, so icon doesnt draw in button */
+	ui_def_but_icon(but, icon, 0);  /* no flag UI_HAS_ICON, so icon doesnt draw in button */
 	but->dragpoin = (void *)path;
 	but->imb = imb;
 	but->imb_scale = scale;
@@ -4220,8 +4227,7 @@ uiBut *uiDefIconTextMenuBut(uiBlock *block, uiMenuCreateFunc func, void *arg, in
 {
 	uiBut *but = ui_def_but(block, UI_BTYPE_PULLDOWN, 0, str, x, y, width, height, arg, 0.0, 0.0, 0.0, 0.0, tip);
 
-	but->icon = (BIFIconID) icon;
-	but->flag |= UI_HAS_ICON;
+	ui_def_but_icon(but, icon, UI_HAS_ICON);
 
 	but->drawflag |= UI_BUT_ICON_LEFT;
 	but->flag |= UI_BUT_ICON_SUBMENU;
@@ -4236,8 +4242,7 @@ uiBut *uiDefIconMenuBut(uiBlock *block, uiMenuCreateFunc func, void *arg, int ic
 {
 	uiBut *but = ui_def_but(block, UI_BTYPE_PULLDOWN, 0, "", x, y, width, height, arg, 0.0, 0.0, 0.0, 0.0, tip);
 
-	but->icon = (BIFIconID) icon;
-	but->flag |= UI_HAS_ICON;
+	ui_def_but_icon(but, icon, UI_HAS_ICON);
 	but->drawflag &= ~UI_BUT_ICON_LEFT;
 
 	but->menu_create_func = func;
@@ -4253,7 +4258,7 @@ uiBut *uiDefIconTextBlockBut(uiBlock *block, uiBlockCreateFunc func, void *arg,
 	
 	/* XXX temp, old menu calls pass on icon arrow, which is now UI_BUT_ICON_SUBMENU flag */
 	if (icon != ICON_RIGHTARROW_THIN) {
-		but->icon = (BIFIconID) icon;
+		ui_def_but_icon(but, icon, 0);
 		but->drawflag |= UI_BUT_ICON_LEFT;
 	}
 	but->flag |= UI_HAS_ICON;
@@ -4270,9 +4275,8 @@ uiBut *uiDefIconBlockBut(uiBlock *block, uiBlockCreateFunc func, void *arg, int
 {
 	uiBut *but = ui_def_but(block, UI_BTYPE_BLOCK, retval, "", x, y, width, height, arg, 0.0, 0.0, 0.0, 0.0, tip);
 	
-	but->icon = (BIFIconID) icon;
-	but->flag |= UI_HAS_ICON;
-	
+	ui_def_but_icon(but, icon, UI_HAS_ICON);
+
 	but->drawflag |= UI_BUT_ICON_LEFT;
 	
 	but->block_create_func = func;
@@ -4305,9 +4309,8 @@ uiBut *uiDefSearchBut(uiBlock *block, void *arg, int retval, int icon, int maxle
 {
 	uiBut *but = ui_def_but(block, UI_BTYPE_SEARCH_MENU, retval, "", x, y, width, height, arg, 0.0, maxlen, a1, a2, tip);
 	
-	but->icon = (BIFIconID) icon;
-	but->flag |= UI_HAS_ICON;
-	
+	ui_def_but_icon(but, icon, UI_HAS_ICON);
+
 	but->drawflag |= UI_BUT_ICON_LEFT | UI_BUT_TEXT_LEFT;
 	
 	ui_but_update(but);