Display a basic list of assets, set up scrolling and notifier listening

* Display a non-interactive list of assets, updates as assets get
  loaded.
* Notifier listening happens via the view, so the grid-view supports
  listening to notifiers. This is what triggers regular redraws as
  assets get loaded.
* Scrolling may need more fine tuning, so that scroll-bars are
  hidden if they don't apply (e.g. don't show horizontal scroll-bar for
  the vertically expanding grid-view layout).

source/blender/editors/include/UI_grid_view.hh

@@ -0,0 +1,49 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+/** \file
+ * \ingroup editorui
+ *
+ * API for simple creation of grid UIs, supporting typically needed features.
+ * https://wiki.blender.org/wiki/Source/Interface/Views/Grid_Views
+ */
+
+#pragma once
+
+struct wmNotifier;
+
+namespace blender::ui {
+
+class AbstractGridViewItem {
+ public:
+  virtual ~AbstractGridViewItem() = default;
+
+ protected:
+  AbstractGridViewItem() = default;
+};
+
+class AbstractGridView {
+ public:
+  virtual ~AbstractGridView() = default;
+
+  /** Listen to a notifier, returning true if a redraw is needed. */
+  virtual bool listen(const wmNotifier &) const;
+
+  // protected:
+  virtual void build() = 0;
+};
+
+}  // namespace blender::ui

source/blender/editors/include/UI_interface.h

@@ -80,6 +80,7 @@ struct wmKeyMapItem;
 struct wmMsgBus;
 struct wmOperator;
 struct wmOperatorType;
+struct wmRegionListenerParams;
 struct wmWindow;
 
 typedef struct uiBlock uiBlock;
@@ -91,6 +92,8 @@ typedef struct uiPopupBlockHandle uiPopupBlockHandle;
 typedef struct uiTreeViewHandle uiTreeViewHandle;
 /* C handle for C++ #ui::AbstractTreeViewItem type. */
 typedef struct uiTreeViewItemHandle uiTreeViewItemHandle;
+/* C handle for C++ #ui::AbstractGridView type. */
+typedef struct uiGridViewHandle uiGridViewHandle;
 
 /* Defines */
 
@@ -3163,6 +3166,9 @@ void UI_interface_tag_script_reload(void);
 /* Support click-drag motion which presses the button and closes a popover (like a menu). */
 #define USE_UI_POPOVER_ONCE
 
+void UI_block_views_listen(const uiBlock *block,
+                           const struct wmRegionListenerParams *listener_params);
+
 bool UI_tree_view_item_is_active(const uiTreeViewItemHandle *item);
 bool UI_tree_view_item_matches(const uiTreeViewItemHandle *a, const uiTreeViewItemHandle *b);
 /**
@@ -3201,6 +3207,11 @@ uiTreeViewItemHandle *UI_block_tree_view_find_item_at(const struct ARegion *regi
                                                       const int xy[2]) ATTR_NONNULL(1, 2);
 uiTreeViewItemHandle *UI_block_tree_view_find_active_item(const struct ARegion *region);
 
+/**
+ * Listen to \a notifier, returning true if the region should redraw.
+ */
+bool UI_grid_view_listen_should_redraw(const uiGridViewHandle *view, const wmNotifier *notifier);
+
 #ifdef __cplusplus
 }
 #endif

source/blender/editors/include/UI_interface.hh

@@ -37,6 +37,7 @@ struct uiSearchItems;
 
 namespace blender::ui {
 
+class AbstractGridView;
 class AbstractTreeView;
 
 /**
@@ -69,6 +70,10 @@ void attribute_search_add_items(
 /**
  * Override this for all available tree types.
  */
+blender::ui::AbstractGridView *UI_block_add_view(
+    uiBlock &block,
+    blender::StringRef idname,
+    std::unique_ptr<blender::ui::AbstractGridView> tree_view);
 blender::ui::AbstractTreeView *UI_block_add_view(
     uiBlock &block,
     blender::StringRef idname,

source/blender/editors/interface/CMakeLists.txt

@@ -38,6 +38,7 @@ set(INC
 )
 
 set(SRC
+  grid_view.cc
   interface.c
   interface_align.c
   interface_anim.c

source/blender/editors/interface/grid_view.cc

@@ -0,0 +1,48 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+/** \file
+ * \ingroup edinterface
+ */
+
+#include "WM_types.h"
+
+#include "UI_interface.h"
+
+#include "UI_grid_view.hh"
+
+namespace blender::ui {
+
+/* ---------------------------------------------------------------------- */
+
+bool AbstractGridView::listen(const wmNotifier &) const
+{
+  /* Nothing by default. */
+  return false;
+}
+
+}  // namespace blender::ui
+
+using namespace blender::ui;
+
+/* ---------------------------------------------------------------------- */
+
+bool UI_grid_view_listen_should_redraw(const uiGridViewHandle *view_handle,
+                                       const wmNotifier *notifier)
+{
+  const AbstractGridView &view = *reinterpret_cast<const AbstractGridView *>(view_handle);
+  return view.listen(*notifier);
+}

source/blender/editors/interface/interface_view.cc

@@ -24,15 +24,22 @@
  */
 
 #include <memory>
+#include <type_traits>
 #include <variant>
 
 #include "DNA_screen_types.h"
 
+#include "BKE_screen.h"
+
 #include "BLI_listbase.h"
 
+#include "ED_screen.h"
+
 #include "interface_intern.h"
 
 #include "UI_interface.hh"
+
+#include "UI_grid_view.hh"
 #include "UI_tree_view.hh"
 
 using namespace blender;
@@ -44,10 +51,11 @@ using namespace blender::ui;
  */
 struct ViewLink : public Link {
   using TreeViewPtr = std::unique_ptr<AbstractTreeView>;
+  using GridViewPtr = std::unique_ptr<AbstractGridView>;
 
   std::string idname;
   /* NOTE: Can't use std::get() on this until minimum macOS deployment target is 10.14. */
-  std::variant<TreeViewPtr> view;
+  std::variant<TreeViewPtr, GridViewPtr> view;
 };
 
 template<class T> T *get_view_from_link(ViewLink &link)
@@ -56,17 +64,32 @@ template<class T> T *get_view_from_link(ViewLink &link)
   return t_uptr ? t_uptr->get() : nullptr;
 }
 
+template<class T>
+static T *ui_block_add_view_impl(uiBlock &block, StringRef idname, std::unique_ptr<T> view)
+{
+  static_assert(std::is_same_v<T, AbstractTreeView> || std::is_same_v<T, AbstractGridView>,
+                "Unsupported view type");
+  ViewLink *view_link = MEM_new<ViewLink>(__func__);
+  BLI_addtail(&block.views, view_link);
+
+  view_link->view = std::move(view);
+  view_link->idname = idname;
+
+  return get_view_from_link<T>(*view_link);
+}
+
+AbstractGridView *UI_block_add_view(uiBlock &block,
+                                    StringRef idname,
+                                    std::unique_ptr<AbstractGridView> tree_view)
+{
+  return ui_block_add_view_impl<AbstractGridView>(block, idname, std::move(tree_view));
+}
+
 AbstractTreeView *UI_block_add_view(uiBlock &block,
                                     StringRef idname,
                                     std::unique_ptr<AbstractTreeView> tree_view)
 {
-  ViewLink *view_link = MEM_new<ViewLink>(__func__);
-  BLI_addtail(&block.views, view_link);
-
-  view_link->view = std::move(tree_view);
-  view_link->idname = idname;
-
-  return get_view_from_link<AbstractTreeView>(*view_link);
+  return ui_block_add_view_impl<AbstractTreeView>(block, idname, std::move(tree_view));
 }
 
 void ui_block_free_views(uiBlock *block)
@@ -76,6 +99,19 @@ void ui_block_free_views(uiBlock *block)
   }
 }
 
+void UI_block_views_listen(const uiBlock *block, const wmRegionListenerParams *listener_params)
+{
+  LISTBASE_FOREACH (ViewLink *, view_link, &block->views) {
+    /* TODO only grid views, should this be supported by all views? */
+    if (AbstractGridView *grid_view = get_view_from_link<AbstractGridView>(*view_link)) {
+      if (UI_grid_view_listen_should_redraw(reinterpret_cast<uiGridViewHandle *>(grid_view),
+                                            listener_params->notifier)) {
+        ED_region_tag_redraw(listener_params->region);
+      }
+    }
+  }
+}
+
 uiTreeViewItemHandle *UI_block_tree_view_find_item_at(const ARegion *region, const int xy[2])
 {
   uiButTreeRow *tree_row_but = (uiButTreeRow *)ui_tree_row_find_mouse_over(region, xy);

source/blender/editors/screen/area.c

@@ -161,6 +161,10 @@ void ED_region_do_listen(wmRegionListenerParams *params)
     region->type->listener(params);
   }
 
+  LISTBASE_FOREACH (uiBlock *, block, &region->uiblocks) {
+    UI_block_views_listen(block, params);
+  }
+
   LISTBASE_FOREACH (uiList *, list, &region->ui_lists) {
     if (list->type && list->type->listener) {
       list->type->listener(list, params);

source/blender/editors/space_assets/asset_browser_draw.cc

@@ -25,6 +25,7 @@
 
 #include "UI_interface.h"
 #include "UI_resources.h"
+#include "UI_view2d.h"
 
 #include "asset_browser_intern.hh"
 #include "asset_view.hh"
@@ -38,9 +39,12 @@ using namespace blender::ed::asset_browser;
 void asset_browser_main_region_draw(const bContext *C, ARegion *region)
 {
   const SpaceAssets *asset_space = CTX_wm_space_assets(C);
+  View2D *v2d = &region->v2d;
 
   UI_ThemeClearColor(TH_BACK);
 
+  UI_view2d_view_ortho(v2d);
+
   const uiStyle *style = UI_style_get_dpi();
   uiBlock *block = UI_block_begin(C, region, __func__, UI_EMBOSS);
   uiLayout *layout = UI_block_layout(block,
@@ -55,6 +59,15 @@ void asset_browser_main_region_draw(const bContext *C, ARegion *region)
 
   asset_view_create_in_layout(*C, asset_space->asset_library_ref, *layout);
 
+  /* Update main region View2d dimensions. */
+  int layout_width, layout_height;
+  UI_block_layout_resolve(block, &layout_width, &layout_height);
+  UI_view2d_totRect_set(v2d, layout_width, layout_height);
+
   UI_block_end(C, block);
   UI_block_draw(C, block);
+
+  /* reset view matrix */
+  UI_view2d_view_restore(C);
+  UI_view2d_scrollers_draw(v2d, nullptr);
 }

source/blender/editors/space_assets/asset_view.cc

@@ -25,23 +25,31 @@
 #include "ED_asset.h"
 
 #include "UI_interface.h"
+#include "UI_interface.hh"
 
 #include "asset_view.hh"
 
+namespace ui = blender::ui;
+
 namespace blender::ed::asset_browser {
 
-AssetGridView::AssetGridView(const AssetLibraryReference &asset_library_ref)
-    : asset_library_ref_(asset_library_ref)
+AssetGridView::AssetGridView(const AssetLibraryReference &asset_library_ref, uiLayout &layout)
+    : asset_library_ref_(asset_library_ref), layout(layout)
 {
 }
 
 void AssetGridView::build()
 {
-  ED_assetlist_iterate(asset_library_ref_, [](AssetHandle asset) {
-    std::cout << ED_asset_handle_get_name(&asset) << std::endl;
+  ED_assetlist_iterate(asset_library_ref_, [this](AssetHandle asset) {
+    uiItemL(
+        &layout, ED_asset_handle_get_name(&asset), ED_asset_handle_get_preview_icon_id(&asset));
     return true;
   });
-  std::cout << std::endl;
+}
+
+bool AssetGridView::listen(const wmNotifier &notifier) const
+{
+  return ED_assetlist_listen(&asset_library_ref_, &notifier);
 }
 
 void asset_view_create_in_layout(const bContext &C,
@@ -55,8 +63,10 @@ void asset_view_create_in_layout(const bContext &C,
 
   UI_block_layout_set_current(block, &layout);
 
-  AssetGridView grid_view{asset_library_ref};
-  grid_view.build();
+  ui::AbstractGridView *grid_view = UI_block_add_view(
+      *block, "asset grid view", std::make_unique<AssetGridView>(asset_library_ref, layout));
+
+  grid_view->build();
 }
 
 }  // namespace blender::ed::asset_browser

source/blender/editors/space_assets/asset_view.hh

@@ -20,19 +20,25 @@
 
 #pragma once
 
+#include "UI_grid_view.hh"
+
 struct bContext;
 struct AssetLibraryReference;
 struct uiLayout;
 
 namespace blender::ed::asset_browser {
 
-class AssetGridView {
+class AssetGridView : public blender::ui::AbstractGridView {
   AssetLibraryReference asset_library_ref_;
 
- public:
-  AssetGridView(const AssetLibraryReference &);
+  /* TODO temp. */
+  uiLayout &layout;
 
-  void build();
+ public:
+  AssetGridView(const AssetLibraryReference &, uiLayout &layout);
+
+  void build() override;
+  bool listen(const wmNotifier &) const override;
 };
 
 void asset_view_create_in_layout(const bContext &C,

source/blender/editors/space_assets/space_assets.cc

@@ -34,6 +34,7 @@
 #include "MEM_guardedalloc.h"
 
 #include "UI_resources.h"
+#include "UI_view2d.h"
 
 #include "asset_browser_intern.hh"
 #include "asset_view.hh"
@@ -57,10 +58,16 @@ static SpaceLink *asset_browser_create(const ScrArea *UNUSED(area), const Scene
   }
 
   {
-    /* Main window. */
+    /* Main region. */
     ARegion *region = MEM_cnew<ARegion>("asset browser main region");
     BLI_addtail(&assets_space->regionbase, region);
     region->regiontype = RGN_TYPE_WINDOW;
+
+    region->v2d.scroll = (V2D_SCROLL_RIGHT | V2D_SCROLL_BOTTOM);
+    region->v2d.align = (V2D_ALIGN_NO_NEG_X | V2D_ALIGN_NO_POS_Y);
+    region->v2d.keepzoom = (V2D_LOCKZOOM_X | V2D_LOCKZOOM_Y | V2D_LIMITZOOM | V2D_KEEPASPECT);
+    region->v2d.keeptot = V2D_KEEPTOT_STRICT;
+    region->v2d.minzoom = region->v2d.maxzoom = 1.0f;
   }
 
   return (SpaceLink *)assets_space;
@@ -90,8 +97,9 @@ static void asset_browser_keymap(wmKeyConfig *UNUSED(keyconf))
 /* ---------------------------------------------------------------------- */
 /* Main Region */
 
-static void asset_browser_main_region_init(wmWindowManager *UNUSED(wm), ARegion *UNUSED(region))
+static void asset_browser_main_region_init(wmWindowManager *UNUSED(wm), ARegion *region)
 {
+  UI_view2d_region_reinit(&region->v2d, V2D_COMMONVIEW_LIST, region->winx, region->winy);
 }
 
 static void asset_browser_main_region_listener(const wmRegionListenerParams *UNUSED(params))

source/blender/editors/util/CMakeLists.txt

@@ -102,6 +102,7 @@ set(SRC
   ../include/ED_uvedit.h
   ../include/ED_view3d.h
   ../include/ED_view3d_offscreen.h
+  ../include/UI_grid_view.hh
   ../include/UI_icons.h
   ../include/UI_interface.h
   ../include/UI_interface.hh