Index: source/blender/makesrna/intern/rna_wm_api.c
===================================================================
--- source/blender/makesrna/intern/rna_wm_api.c	(revision 27619)
+++ source/blender/makesrna/intern/rna_wm_api.c	(working copy)
@@ -208,6 +208,11 @@
 	RNA_def_function_ui_description(func, "Operator popup invoke.");
 	rna_generic_op_invoke(func, 1, 1);
 
+	/* invoked dialog opens popup with OK button, does not auto-exec operator. */
+	func= RNA_def_function(srna, "invoke_props_dialog", "WM_operator_props_dialog_popup");
+	RNA_def_function_ui_description(func, "Operator dialog (non-autoexec popup) invoke.");
+	rna_generic_op_invoke(func, 0, 0);
+
 	/* invoke enum */
 	func= RNA_def_function(srna, "invoke_search_popup", "rna_Operator_enum_search_invoke");
 	rna_generic_op_invoke(func, 0, 0);
Index: source/blender/windowmanager/intern/wm_operators.c
===================================================================
--- source/blender/windowmanager/intern/wm_operators.c	(revision 27619)
+++ source/blender/windowmanager/intern/wm_operators.c	(working copy)
@@ -910,7 +910,60 @@
 	return block;
 }
 
+/* Only invoked by OK button in popups created with wm_block_create_dialog() */
+static void dialog_exec_cb(bContext *C, void *arg1, void *arg2)
+{
+	wmOperator *op= arg1;
+	uiBlock *block= arg2;
 
+	WM_operator_call(C, op);
+
+	uiPupBlockClose(C, block);
+}
+
+/* Dialogs are popups that require user verification (click OK) before exec */
+static uiBlock *wm_block_create_dialog(bContext *C, ARegion *ar, void *arg_op)
+{
+	wmWindowManager *wm= CTX_wm_manager(C);
+	wmOperator *op= arg_op;
+	PointerRNA ptr;
+	uiBlock *block;
+	uiLayout *layout;
+	uiBut *btn;
+	uiStyle *style= U.uistyles.first;
+	int columns= 2, width=300;
+
+	block = uiBeginBlock(C, ar, "operator dialog", UI_EMBOSS);
+	uiBlockClearFlag(block, UI_BLOCK_LOOP);
+	uiBlockSetFlag(block, UI_BLOCK_KEEP_OPEN|UI_BLOCK_RET_1|UI_BLOCK_MOVEMOUSE_QUIT);
+
+	if (!op->properties) {
+		IDPropertyTemplate val = {0};
+		op->properties= IDP_New(IDP_GROUP, val, "wmOperatorProperties");
+	}
+
+	RNA_pointer_create(&wm->id, op->type->srna, op->properties, &ptr);
+	layout= uiBlockLayout(block, UI_LAYOUT_VERTICAL, UI_LAYOUT_PANEL, 0, 0, width, 20, style);
+	uiItemL(layout, op->type->name, 0);
+
+	if (op->type->ui) {
+		op->layout= layout;
+		op->type->ui((bContext*)C, op);
+		op->layout= NULL;
+	}
+	else
+		uiDefAutoButsRNA(C, layout, &ptr, columns);
+
+	/* Create OK button, the callback of which will execute op */
+	btn= uiDefBut(block, BUT, 0, "OK", 0, 0, 0, 20, NULL, 0, 0, 0, 0, "");
+	uiButSetFunc(btn, dialog_exec_cb, op, block);
+
+	uiPopupBoundsBlock(block, 4.0f, 0, 0);
+	uiEndBlock(C, block);
+
+	return block;
+}
+
 static uiBlock *wm_operator_create_ui(bContext *C, ARegion *ar, void *userData)
 {
 	struct { wmOperator *op; int width; int height; } * data = userData;
@@ -958,6 +1011,14 @@
 	return retval;
 }
 
+int WM_operator_props_dialog_popup(bContext *C, wmOperator *op, wmEvent *event)
+{
+	/* op is not executed until popup OK but is clicked */
+	uiPupBlock(C, wm_block_create_dialog, op);
+
+	return OPERATOR_RUNNING_MODAL;
+}
+
 void WM_operator_ui_popup(bContext *C, wmOperator *op, int width, int height)
 {
 	struct { wmOperator *op; int width; int height; } data;