Add multi-view workspace and shared library

Introduce MultiViewWorkspace and ImageLibraryState to support multiple image view windows and a shared loaded-image queue/recent list. Update many APIs and actions to accept the shared ImageLibraryState (and viewer lists where needed), move loaded-image and recent-image management into the shared library, and keep per-view interaction state in ViewerState. Add an Image List window UI, new view creation (double-click/new view), menu shortcuts, drag-and-drop handling, and per-workspace sync logic. Add a multi-view regression test and helper script, update CMake and README/docs to describe the feature, and adjust rendering/windowing code to handle multiple Image N windows and docking behavior. Note: preview controls (exposure, gamma, OCIO, etc.) remain global and are left for a follow-up.

Author: ssh4net

src/doc/imiv_dev.rst

@@ -188,19 +188,38 @@ new work easier to reason about.
 `ViewerState`
 -------------
 
-`ViewerState` in `src/imiv/imiv_viewer.h` is the runtime model for the loaded
-image and its current interaction state. It owns:
+`ViewerState` in `src/imiv/imiv_viewer.h` is the per-view runtime model for the
+currently displayed image and its interaction state. It owns:
 
 * the current `LoadedImage`;
 * status and error text;
 * zoom, scroll, zoom pivot, and fit behavior;
 * selection and area-probe state;
-* the loaded-image list and recent-image list;
+* the current loaded-image index within the shared library;
 * windowed/fullscreen placement;
 * the current `RendererTexture`.
 
-If state is tied to the currently loaded image or to navigation through that
-image, it usually belongs here.
+If state is tied to one image pane and its navigation state, it usually
+belongs here.
+
+`ImageLibraryState` and `MultiViewWorkspace`
+--------------------------------------------
+
+The first multi-view slice introduces two more shared state buckets in
+`src/imiv/imiv_viewer.h`:
+
+* `ImageLibraryState`
+  owns the shared loaded-image queue, recent-image history, and sort mode;
+* `MultiViewWorkspace`
+  owns the open image windows, the active view id, and Image List visibility.
+
+Each `ImageViewWindow` owns one `ViewerState`. The main `Image` window is the
+primary view. Additional `Image N` windows are created from
+`File -> New view from current image` or by double-clicking entries in the
+Image List window.
+
+This split matters: queue history is now global to the workspace, but image
+interaction state remains per view.
 
 `PlaceholderUiState`
 --------------------
@@ -217,6 +236,12 @@ image, it usually belongs here.
 If state describes how the UI should look or how preview rendering should be
 configured across launches, it usually belongs here.
 
+At the moment, this also means preview controls are still shared across all
+open image views. Exposure, gamma, offset, interpolation, and OCIO selection
+remain global UI state rather than per-view state. Splitting those controls
+into per-view state is a follow-up task, not part of the first multi-view
+milestone.
+
 `DeveloperUiState`
 ------------------
 
@@ -241,8 +266,8 @@ layout state together in a single `imiv.inf` file.
 
 * the Dear ImGui `.ini` text first, straight from
   `ImGui::SaveIniSettingsToMemory()`;
-* then an `ImivApp` settings section with `PlaceholderUiState` and a small
-  amount of `ViewerState`.
+* then an `ImivApp` settings section with `PlaceholderUiState`,
+  `ImageLibraryState`, and a small amount of `ViewerState`.
 
 This is worth preserving. It gives :program:`imiv` one file for:
 
@@ -273,10 +298,11 @@ The current order is:
 6. execute queued state mutations with `execute_viewer_frame_actions()`;
 7. process drag and drop and auto-subimage work;
 8. clamp UI state;
-9. update the renderer preview texture from the current preview controls;
+9. update the renderer preview texture for the active view from the current
+   preview controls;
 10. build the dockspace host window;
-11. draw the main image window;
-12. draw auxiliary windows and popups;
+11. draw the main image window and any secondary `Image N` windows;
+12. draw the Image List window, auxiliary windows, and popups;
 13. draw developer-mode Dear ImGui diagnostic windows and the drag overlay.
 
 Two design choices here are important:
@@ -309,6 +335,14 @@ The main image window:
 * is assigned to the dockspace with `ImGui::SetNextWindowDockID()`;
 * uses `ImGuiWindowClass` to request `ImGuiDockNodeFlags_AutoHideTabBar`.
 
+Secondary image windows:
+
+* are named `Image N`;
+* are created as ordinary Dear ImGui windows with the same image-window class;
+* are forced into the main dockspace on first creation;
+* currently use `ImGuiDockNodeFlags_NoUndocking`;
+* inherit the same shared preview/renderer policy as the primary view.
+
 Why there is no `DockBuilder`
 -----------------------------
 
@@ -331,6 +365,8 @@ The main windows are:
 
 * the dockspace host window;
 * the `Image` window;
+* zero or more `Image N` windows;
+* `Image List`;
 * `iv Info`;
 * `iv Preferences`;
 * `Preview`;

src/doc/imiv_tests.rst

@@ -260,6 +260,7 @@ already includes fields such as:
 
 * `image_loaded`, `image_path`, `zoom`, and `fit_image_to_window`
 * selection and Area Sample state
+* multi-view state (`view_count`, `active_view_id`, `active_view_docked`)
 * backend state (`active`, `requested`, `next_launch`, compiled backends)
 * OCIO state (requested source, resolved source, resolved config path,
   display/view, available menus)
@@ -270,6 +271,9 @@ Example excerpt::
       "image_loaded": true,
       "zoom": 1.000000,
       "selection_active": false,
+      "view_count": 2,
+      "active_view_id": 2,
+      "active_view_docked": true,
       "backend": {
         "active": "vulkan",
         "requested": "auto",
@@ -355,6 +359,10 @@ Run a focused UI regression::
 
     ctest --test-dir build_u -V -R '^imiv_ux_actions_regression$'
 
+Run the focused multi-view regression::
+
+    ctest --test-dir build_u -V -R '^imiv_multiview_regression$'
+
 Run the backend-preference regression::
 
     ctest --test-dir build_u -V -R '^imiv_backend_preferences_regression$'

src/doc/imiv_user.rst

@@ -177,6 +177,36 @@ Common shortcuts:
 The `Tools` menu also exposes slideshow, sort-order, and orientation actions.
 
 
+Multiple views and image list
+=============================
+
+The current multi-view workflow is centered on shared loaded-image history and
+per-window image panes.
+
+Useful actions:
+
+* `File -> New view from current image`
+  duplicates the current image into a new `Image N` window.
+* `View -> Image List`
+  opens a dockable window showing the current loaded-image queue.
+
+The `Image List` window currently supports:
+
+* single-click
+  load the chosen image into the active image view;
+* double-click
+  open the chosen image in a new image view window.
+
+The main `Image` window remains the primary docked image pane. Additional
+`Image N` windows are currently created docked into the main dockspace.
+Undocking those image views is intentionally disabled in this first slice.
+
+This is the first multi-view milestone. View windows already have independent
+loaded images, zoom, scroll, and selection state, but preview controls are
+still shared. Exposure, gamma, offset, interpolation, and OCIO display/view
+choices are not yet stored per window.
+
+
 Color management
 ================
 
@@ -248,10 +278,12 @@ Current limitations
 
 At the time of this writing, notable differences from :program:`iv` include:
 
-* `Move to new window` is still a placeholder action.
 * Fullscreen behavior does not yet exactly match :program:`iv`.
 * Opening the same file repeatedly does not currently create duplicate loaded
   image entries.
+* Multi-view image windows are available, but preview controls such as
+  exposure, gamma, offset, interpolation, and OCIO display/view are still
+  shared state rather than per-view state.
 * Some older :program:`iv` mouse modes are not yet a priority for the Dear
   ImGui port.
 

src/imiv/CMakeLists.txt

@@ -1315,6 +1315,22 @@ if (TARGET imiv
             LABELS "imiv;gui"
             TIMEOUT 360)
 
+    add_test (
+        NAME imiv_multiview_regression
+        COMMAND
+            "${Python3_EXECUTABLE}"
+            "${CMAKE_CURRENT_SOURCE_DIR}/tools/imiv_multiview_regression.py"
+            --bin "$<TARGET_FILE:imiv>"
+            --cwd "$<TARGET_FILE_DIR:imiv>"
+            ${_imiv_ctest_default_backend_args}
+            --env-script "${CMAKE_BINARY_DIR}/imiv_env.sh"
+            --out-dir "${CMAKE_BINARY_DIR}/imiv_captures/multiview_regression"
+            --open "${PROJECT_SOURCE_DIR}/ASWF/logos/openimageio-stacked-gradient.png")
+    set_tests_properties (
+        imiv_multiview_regression PROPERTIES
+            LABELS "imiv;gui;imiv_multiview"
+            TIMEOUT 180)
+
     add_test (
         NAME imiv_rgb_input_regression
         COMMAND

src/imiv/README.md

@@ -114,6 +114,12 @@ Focused backend-selector regression from a multi-backend build:
 ctest --test-dir build_u -V -R '^imiv_backend_preferences_regression$'
 ```
 
+Focused multi-view regression:
+
+```bash
+ctest --test-dir build_u -V -R '^imiv_multiview_regression$'
+```
+
 Focused developer-menu regression:
 
 ```bash