source/blender/editors/interface/interface_panel.cc

@@ -1298,11 +1298,9 @@ void UI_panel_category_draw_all(ARegion *region, const char *category_id_active)
   const int roundboxtype = is_left ? (UI_CNR_TOP_LEFT | UI_CNR_BOTTOM_LEFT) :
                                      (UI_CNR_TOP_RIGHT | UI_CNR_BOTTOM_RIGHT);
   bool is_alpha;
-  bool do_scaletabs = false;
 #ifdef USE_FLAT_INACTIVE
   bool is_active_prev = false;
 #endif
-  float scaletabs = 1.0f;
   /* Same for all tabs. */
   /* Intentionally don't scale by 'px'. */
   const int rct_xmin = is_left ? v2d->mask.xmin + 3 : (v2d->mask.xmax - category_tabs_width);
@@ -1344,7 +1342,7 @@ void UI_panel_category_draw_all(ARegion *region, const char *category_id_active)
     BLI_assert(UI_panel_category_is_visible(region));
   }
 
-  /* Calculate tab rectangle and check if we need to scale down. */
+  /* Calculate tab rectangle for each panel. */
   LISTBASE_FOREACH (PanelCategoryDyn *, pc_dyn, &region->panels_category) {
     rcti *rct = &pc_dyn->rect;
     const char *category_id = pc_dyn->idname;
@@ -1360,16 +1358,13 @@ void UI_panel_category_draw_all(ARegion *region, const char *category_id_active)
     y_ofs += category_width + tab_v_pad + (tab_v_pad_text * 2);
   }
 
-  if (y_ofs > BLI_rcti_size_y(&v2d->mask)) {
+  const int max_scroll = max_ii(y_ofs - BLI_rcti_size_y(&v2d->mask), 0);
-    scaletabs = float(BLI_rcti_size_y(&v2d->mask)) / float(y_ofs);
+  const int scroll = clamp_i(region->category_scroll, 0, max_scroll);
-
+  region->category_scroll = scroll;
-    LISTBASE_FOREACH (PanelCategoryDyn *, pc_dyn, &region->panels_category) {
+  LISTBASE_FOREACH (PanelCategoryDyn *, pc_dyn, &region->panels_category) {
-      rcti *rct = &pc_dyn->rect;
+    rcti *rct = &pc_dyn->rect;
-      rct->ymin = ((rct->ymin - v2d->mask.ymax) * scaletabs) + v2d->mask.ymax;
+    rct->ymin += scroll;
-      rct->ymax = ((rct->ymax - v2d->mask.ymax) * scaletabs) + v2d->mask.ymax;
+    rct->ymax += scroll;
-    }
-
-    do_scaletabs = true;
   }
 
   /* Begin drawing. */
@@ -1405,14 +1400,17 @@ void UI_panel_category_draw_all(ARegion *region, const char *category_id_active)
 
   LISTBASE_FOREACH (PanelCategoryDyn *, pc_dyn, &region->panels_category) {
     const rcti *rct = &pc_dyn->rect;
+    if (rct->ymin > v2d->mask.ymax) {
+      /* Scrolled outside the top of the view, check the next tab. */
+      continue;
+    }
+    if (rct->ymax < v2d->mask.ymin) {
+      /* Scrolled past visible bounds, no need to draw other tabs. */
+      break;
+    }
     const char *category_id = pc_dyn->idname;
     const char *category_id_draw = IFACE_(category_id);
-    const int category_width = BLI_rcti_size_y(rct) - (tab_v_pad_text * 2);
     size_t category_draw_len = BLF_DRAW_STR_DUMMY_MAX;
-#if 0
-    int category_width = BLF_width(fontid, category_id_draw, BLF_DRAW_STR_DUMMY_MAX);
-#endif
-
     const bool is_active = STREQ(category_id, category_id_active);
 
     GPU_blend(GPU_BLEND_ALPHA);
@@ -1469,11 +1467,6 @@ void UI_panel_category_draw_all(ARegion *region, const char *category_id_active)
 
     /* Tab titles. */
 
-    if (do_scaletabs) {
-      category_draw_len = BLF_width_to_strlen(
-          fontid, category_id_draw, category_draw_len, category_width, nullptr);
-    }
-
     BLF_position(fontid, rct->xmax - text_v_ofs, rct->ymin + tab_v_pad_text, 0.0f);
     BLF_color3ubv(fontid, is_active ? theme_col_text_hi : theme_col_text);
     BLF_draw(fontid, category_id_draw, category_draw_len);
@@ -2255,7 +2248,9 @@ static int ui_handle_panel_category_cycling(const wmEvent *event,
     const char *category = UI_panel_category_active_get(region, false);
     if (LIKELY(category)) {
       PanelCategoryDyn *pc_dyn = UI_panel_category_find(region, category);
-      if (LIKELY(pc_dyn)) {
+      /* Cyclic behavior between categories
+       * using Ctrl+Tab (+Shift for backwards) or Ctrl+Wheel Up/Down. */
+      if (LIKELY(pc_dyn) && (event->modifier & KM_CTRL)) {
         if (is_mousewheel) {
           /* We can probably get rid of this and only allow Ctrl-Tabbing. */
           pc_dyn = (event->type == WHEELDOWNMOUSE) ? pc_dyn->next : pc_dyn->prev;
@@ -2276,9 +2271,9 @@ static int ui_handle_panel_category_cycling(const wmEvent *event,
           UI_panel_category_active_set(region, pc_dyn->idname);
           ED_region_tag_redraw(region);
         }
+        return WM_UI_HANDLER_BREAK;
       }
     }
-    return WM_UI_HANDLER_BREAK;
   }
 
   return WM_UI_HANDLER_CONTINUE;

source/blender/editors/interface/view2d_ops.cc

@@ -82,6 +82,9 @@ struct v2dViewPanData {
   /** event starting pan, for modal exit */
   int invoke_event;
 
+  /** Tag if the scroll is done in the category tab. */
+  bool do_category_scroll;
+
   /** for MMB in scrollers (old feature in past, but now not that useful) */
   short in_scroller;
 
@@ -133,6 +136,8 @@ static void view_pan_init(bContext *C, wmOperator *op)
   vpd->facy = BLI_rctf_size_y(&vpd->v2d->cur) / winy;
 
   vpd->v2d->flag |= V2D_IS_NAVIGATING;
+
+  vpd->do_category_scroll = false;
 }
 
 /* apply transform to view (i.e. adjust 'cur' rect) */
@@ -144,14 +149,19 @@ static void view_pan_apply_ex(bContext *C, v2dViewPanData *vpd, float dx, float
   dx *= vpd->facx;
   dy *= vpd->facy;
 
-  /* only move view on an axis if change is allowed */
+  if (!vpd->do_category_scroll) {
-  if ((v2d->keepofs & V2D_LOCKOFS_X) == 0) {
+    /* only move view on an axis if change is allowed */
-    v2d->cur.xmin += dx;
+    if ((v2d->keepofs & V2D_LOCKOFS_X) == 0) {
-    v2d->cur.xmax += dx;
+      v2d->cur.xmin += dx;
+      v2d->cur.xmax += dx;
+    }
+    if ((v2d->keepofs & V2D_LOCKOFS_Y) == 0) {
+      v2d->cur.ymin += dy;
+      v2d->cur.ymax += dy;
+    }
   }
-  if ((v2d->keepofs & V2D_LOCKOFS_Y) == 0) {
+  else {
-    v2d->cur.ymin += dy;
+    vpd->region->category_scroll -= dy;
-    v2d->cur.ymax += dy;
   }
 
   /* Inform v2d about changes after this operation. */
@@ -212,6 +222,8 @@ static int view_pan_invoke(bContext *C, wmOperator *op, const wmEvent *event)
   vpd->starty = vpd->lasty = event->xy[1];
   vpd->invoke_event = event->type;
 
+  vpd->do_category_scroll = ED_region_panel_category_gutter_isect_xy(vpd->region, event->xy);
+
   if (event->type == MOUSEPAN) {
     RNA_int_set(op->ptr, "deltax", event->prev_xy[0] - event->xy[0]);
     RNA_int_set(op->ptr, "deltay", event->prev_xy[1] - event->xy[1]);
@@ -482,6 +494,10 @@ static int view_scrolldown_exec(bContext *C, wmOperator *op)
     return OPERATOR_PASS_THROUGH;
   }
 
+  const wmWindow *win = CTX_wm_window(C);
+  vpd->do_category_scroll = ED_region_panel_category_gutter_isect_xy(vpd->region,
+                                                                     win->eventstate->xy);
+
   /* set RNA-Props */
   RNA_int_set(op->ptr, "deltax", 0);
   RNA_int_set(op->ptr, "deltay", -40);
@@ -529,6 +545,10 @@ static int view_scrollup_exec(bContext *C, wmOperator *op)
     return OPERATOR_PASS_THROUGH;
   }
 
+  const wmWindow *win = CTX_wm_window(C);
+  vpd->do_category_scroll = ED_region_panel_category_gutter_isect_xy(vpd->region,
+                                                                     win->eventstate->xy);
+
   /* set RNA-Props */
   RNA_int_set(op->ptr, "deltax", 0);
   RNA_int_set(op->ptr, "deltay", 40);
@@ -2181,6 +2201,8 @@ static int reset_exec(bContext *C, wmOperator * /*op*/)
   View2D *v2d = &region->v2d;
   const int snap_test = ED_region_snap_size_test(region);
 
+  region->category_scroll = 0;
+
   /* zoom 1.0 */
   const int winx = float(BLI_rcti_size_x(&v2d->mask) + 1);
   const int winy = float(BLI_rcti_size_y(&v2d->mask) + 1);

source/blender/makesdna/DNA_screen_types.h

@@ -455,6 +455,10 @@ typedef struct ARegion {
   rcti drawrct;
   /** Size. */
   short winx, winy;
+  /* This is a Y offset on the panel tabs that represents pixels, where zero represents no scroll -
+   * the first category always shows first at the top. */
+  int category_scroll;
+  char _pad0[4];
 
   /** Region is currently visible on screen. */
   short visible;