Add drag-resize to uiTemplatePreview (mat/tex/etc. preview widget).

This is done by adding a new button type, GRIP, similar to other numbuttons
(scroll, slider, ...), which here controls the preview height.

Then, we add a new DNA struct to be able to save that height in Blend files
(note I choose not to use Panel struct for this, because we would then have the
same limitation we used to have with uiLists, only one preview per panel
and no preview outside panel).

This implies a change to template_preview UI RNA/py API (each preview needs an ID),
but this is backward compatible, as by default datablock type will be used if no ID is
given (which means e.g. all material previews with no ID will have same height).

Reviewers: brecht

Reviewed By: brecht

Differential Revision: https://developer.blender.org/D342

1 files changed, 38 insertions, 4 deletions

diff --git a/source/blender/editors/interface/interface_templates.c b/source/blender/editors/interface/interface_templates.c
index a4937514a9d..9fd8acce3ee 100644
--- a/source/blender/editors/interface/interface_templates.c
+++ b/source/blender/editors/interface/interface_templates.c
@@ -55,6 +55,7 @@
 #include "BKE_displist.h"
 #include "BKE_dynamicpaint.h"
 #include "BKE_global.h"
+#include "BKE_idcode.h"
 #include "BKE_library.h"
 #include "BKE_main.h"
 #include "BKE_material.h"
@@ -1290,10 +1291,14 @@ static void do_preview_buttons(bContext *C, void *arg, int event)
 	}
 }
 
-void uiTemplatePreview(uiLayout *layout, ID *id, int show_buttons, ID *parent, MTex *slot)
+void uiTemplatePreview(uiLayout *layout, bContext *C, ID *id, int show_buttons, ID *parent, MTex *slot,
+                       const char *preview_id)
 {
 	uiLayout *row, *col;
 	uiBlock *block;
+	uiPreview *ui_preview = NULL;
+	ARegion *ar;
+
 	Material *ma = NULL;
 	Tex *tex = (Tex *)id;
 	ID *pid, *pparent;
@@ -1301,6 +1306,8 @@ void uiTemplatePreview(uiLayout *layout, ID *id, int show_buttons, ID *parent, M
 	PointerRNA material_ptr;
 	PointerRNA texture_ptr;
 
+	char _preview_id[UI_MAX_NAME_STR];
+
 	if (id && !ELEM4(GS(id->name), ID_MA, ID_TE, ID_WO, ID_LA)) {
 		RNA_warning("Expected ID of type material, texture, lamp or world");
 		return;
@@ -1326,17 +1333,44 @@ void uiTemplatePreview(uiLayout *layout, ID *id, int show_buttons, ID *parent, M
 		}
 	}
 
+	if (!preview_id || (preview_id[0] == '\0')) {
+		/* If no identifier given, generate one from ID type. */
+		BLI_snprintf(_preview_id, UI_MAX_NAME_STR, "uiPreview_%s", BKE_idcode_to_name(GS(id->name)));
+		preview_id = _preview_id;
+	}
+
+	/* Find or add the uiPreview to the current Region. */
+	ar = CTX_wm_region(C);
+	ui_preview = BLI_findstring(&ar->ui_previews, preview_id, offsetof(uiPreview, preview_id));
+
+	if (!ui_preview) {
+		ui_preview = MEM_callocN(sizeof(uiPreview), "uiPreview");
+		BLI_strncpy(ui_preview->preview_id, preview_id, sizeof(ui_preview->preview_id));
+		ui_preview->height = (short)(UI_UNIT_Y * 5.6f);
+		BLI_addtail(&ar->ui_previews, ui_preview);
+	}
+
+	if (ui_preview->height < UI_UNIT_Y) {
+		ui_preview->height = UI_UNIT_Y;
+	}
+	else if (ui_preview->height > UI_UNIT_Y * 50) {  /* Rather high upper limit, yet not insane! */
+		ui_preview->height = UI_UNIT_Y * 50;
+	}
+
 	/* layout */
 	block = uiLayoutGetBlock(layout);
 	row = uiLayoutRow(layout, false);
 	col = uiLayoutColumn(row, false);
 	uiLayoutSetKeepAspect(col, true);
-	
+
 	/* add preview */
-	uiDefBut(block, BUT_EXTRA, 0, "", 0, 0, UI_UNIT_X * 6, UI_UNIT_Y * 6, pid, 0.0, 0.0, 0, 0, "");
+	uiDefBut(block, BUT_EXTRA, 0, "", 0, 0, UI_UNIT_X * 10, ui_preview->height, pid, 0.0, 0.0, 0, 0, "");
 	uiBlockSetDrawExtraFunc(block, ED_preview_draw, pparent, slot);
 	uiBlockSetHandleFunc(block, do_preview_buttons, NULL);
-	
+
+	uiDefIconButS(block, GRIP, 0, ICON_GRIP, 0, 0, UI_UNIT_X * 10, (short)(UI_UNIT_Y * 0.3f), &ui_preview->height,
+	              UI_UNIT_Y, UI_UNIT_Y * 50.0f, 0.0f, 0.0f, "");
+
 	/* add buttons */
 	if (pid && show_buttons) {
 		if (GS(pid->name) == ID_MA || (pparent && GS(pparent->name) == ID_MA)) {