2 files changed, 24 insertions, 1 deletions

diff --git a/src/ui/util.c b/src/ui/util.c
index 9aa634bc..0af33138 100644
--- a/src/ui/util.c
+++ b/src/ui/util.c
@@ -62,6 +62,19 @@ int keyMods_Sym(int kmods) {
     return kmods;
 }
 
+iRangei intersect_Rangei(iRangei a, iRangei b) {
+    if (a.end < b.start || a.start > b.end) {
+        return (iRangei){ 0, 0 };
+    }
+    return (iRangei){ iMax(a.start, b.start), iMin(a.end, b.end) };
+}
+
+iRangei union_Rangei(iRangei a, iRangei b) {
+    if (isEmpty_Rangei(a)) return b;
+    if (isEmpty_Rangei(b)) return a;
+    return (iRangei){ iMin(a.start, b.start), iMax(a.end, b.end) };
+}
+
 /*-----------------------------------------------------------------------------------------------*/
 
 void init_Click(iClick *d, iAnyObject *widget, int button) {
diff --git a/src/ui/util.h b/src/ui/util.h
index ae3742b5..468f2057 100644
--- a/src/ui/util.h
+++ b/src/ui/util.h
@@ -48,7 +48,17 @@ iLocalDef iBool isResize_UserEvent(const SDL_Event *d) {
 #   define KMOD_SECONDARY   KMOD_GUI
 #endif
 
-int     keyMods_Sym         (int kmods); /* shift, alt, control, or gui */
+int         keyMods_Sym         (int kmods); /* shift, alt, control, or gui */
+
+iRangei     intersect_Rangei    (iRangei a, iRangei b);
+iRangei     union_Rangei        (iRangei a, iRangei b);
+
+iLocalDef iBool equal_Rangei(iRangei a, iRangei b) {
+    return a.start == b.start && a.end == b.end;
+}
+iLocalDef iBool isEmpty_Rangei(iRangei d) {
+    return size_Range(&d) == 0;
+}
 
 /*-----------------------------------------------------------------------------------------------*/