When explicitly regenerating groups, only generate until active group.

Before this change, groups and their meshes were generated even past
the active group, which, in cause the mesh was broken, caused red
marks to appear for no apparent reason. Furthermore, it unnecessarily
slows down regeneration.

src/dsc.h

@@ -304,6 +304,22 @@ public:
         return t;
     }
 
+    int IndexOf(H h) {
+        int first = 0, last = n-1;
+        while(first <= last) {
+            int mid = (first + last)/2;
+            H hm = elem[mid].h;
+            if(hm.v > h.v) {
+                last = mid-1; // and first stays the same
+            } else if(hm.v < h.v) {
+                first = mid+1; // and last stays the same
+            } else {
+                return mid;
+            }
+        }
+        return -1;
+    }
+
     T *FindByIdNoOops(H h) {
         int first = 0, last = n-1;
         while(first <= last) {

src/generate.cpp

@@ -168,6 +168,12 @@ void SolveSpaceUI::GenerateAll(void) {
 void SolveSpaceUI::GenerateAll(int first, int last, bool andFindFree) {
     int i, j;
 
+    // generate until active group
+    if(last == -2) {
+        last = SK.group.IndexOf(SS.GW.activeGroup);
+        if(last == -1) last = INT_MAX;
+    }
+
     // Remove any requests or constraints that refer to a nonexistent
     // group; can check those immediately, since we know what the list
     // of groups should be.

src/graphicswin.cpp

@@ -886,7 +886,7 @@ void GraphicsWindow::MenuEdit(int id) {
 
         case MNU_REGEN_ALL:
             SS.ReloadAllImported();
-            SS.GenerateAll(0, INT_MAX);
+            SS.GenerateAll(0, -2);
             SS.ScheduleShowTW();
             break;