Add multi-backend renderer selection & GLFW layer

Introduce selectable renderer backends (auto, vulkan, metal, opengl) in CMake and wire up a GLFW platform abstraction. Adds imiv_platform_glfw (platform_glfw_* APIs) and renderer backend files/headers (including imiv_renderer_backend.h, metal/opengl/vulkan sources) and reorganizes source lists and ImGui backend selection. Refactors imiv_app, imiv_actions, imiv_frame and related headers to use the new platform and renderer abstractions, replaces direct GLFW/ImGui/Vulkan calls with platform_glfw_* and renderer_* helpers, and updates build/link logic for each backend. Also adds imiv_upload_types, tweaks OCIO uniform API (PreviewControls -> RendererPreviewControls), and includes various build checks and messages to ensure correct backend selection and platform requirements (e.g. Metal on Apple). This enables cleaner multi-backend support and isolates GLFW/platform-specific behavior.

Author: ssh4net

src/imiv/CMakeLists.txt

@@ -28,13 +28,54 @@ option (OIIO_IMIV_ADD_UPLOAD_SMOKE_CTEST
         "Add an optional CTest entry that generates/upload-tests the imiv corpus" OFF)
 set (OIIO_IMIV_VULKAN_SDK "$ENV{VULKAN_SDK}" CACHE PATH
      "Optional Vulkan SDK root path used to locate Vulkan package for imiv")
+set (_imiv_default_renderer "vulkan")
+if (APPLE)
+    set (_imiv_default_renderer "metal")
+endif ()
+set (OIIO_IMIV_RENDERER "auto" CACHE STRING
+     "Renderer backend for imiv (auto, vulkan, metal, opengl)")
+set_property (CACHE OIIO_IMIV_RENDERER PROPERTY STRINGS
+              auto vulkan metal opengl)
 
 check_is_enabled (imiv imiv_enabled)
 if (NOT imiv_enabled)
     message (STATUS "Disabling imiv")
     return ()
 endif ()
 
+string (TOLOWER "${OIIO_IMIV_RENDERER}" _imiv_renderer_request)
+if (_imiv_renderer_request STREQUAL ""
+    OR _imiv_renderer_request STREQUAL "auto")
+    set (_imiv_selected_renderer "${_imiv_default_renderer}")
+elseif (_imiv_renderer_request STREQUAL "vulkan"
+        OR _imiv_renderer_request STREQUAL "metal"
+        OR _imiv_renderer_request STREQUAL "opengl")
+    set (_imiv_selected_renderer "${_imiv_renderer_request}")
+else ()
+    message (FATAL_ERROR
+             "imiv: unsupported OIIO_IMIV_RENDERER='${OIIO_IMIV_RENDERER}' "
+             "(expected auto, vulkan, metal, or opengl)")
+endif ()
+
+if (_imiv_selected_renderer STREQUAL "metal" AND NOT APPLE)
+    message (FATAL_ERROR
+             "imiv: OIIO_IMIV_RENDERER=metal requires APPLE")
+endif ()
+
+set (_imiv_renderer_is_vulkan OFF)
+set (_imiv_renderer_is_metal OFF)
+set (_imiv_renderer_is_opengl OFF)
+if (_imiv_selected_renderer STREQUAL "vulkan")
+    set (_imiv_renderer_is_vulkan ON)
+elseif (_imiv_selected_renderer STREQUAL "metal")
+    set (_imiv_renderer_is_metal ON)
+elseif (_imiv_selected_renderer STREQUAL "opengl")
+    set (_imiv_renderer_is_opengl ON)
+endif ()
+
+message (STATUS
+         "imiv: selected renderer backend = glfw+${_imiv_selected_renderer}")
+
 set (_imiv_imgui_required_files
      "${OIIO_IMIV_IMGUI_ROOT}/imgui.h"
      "${OIIO_IMIV_IMGUI_ROOT}/imgui.cpp"
@@ -43,10 +84,25 @@ set (_imiv_imgui_required_files
      "${OIIO_IMIV_IMGUI_ROOT}/imgui_widgets.cpp"
      "${OIIO_IMIV_IMGUI_ROOT}/backends/imgui_impl_glfw.h"
      "${OIIO_IMIV_IMGUI_ROOT}/backends/imgui_impl_glfw.cpp")
-if (NOT APPLE)
+set (_imiv_imgui_renderer_sources)
+if (_imiv_renderer_is_vulkan)
     list (APPEND _imiv_imgui_required_files
           "${OIIO_IMIV_IMGUI_ROOT}/backends/imgui_impl_vulkan.h"
           "${OIIO_IMIV_IMGUI_ROOT}/backends/imgui_impl_vulkan.cpp")
+    list (APPEND _imiv_imgui_renderer_sources
+          "${OIIO_IMIV_IMGUI_ROOT}/backends/imgui_impl_vulkan.cpp")
+elseif (_imiv_renderer_is_metal)
+    list (APPEND _imiv_imgui_required_files
+          "${OIIO_IMIV_IMGUI_ROOT}/backends/imgui_impl_metal.h"
+          "${OIIO_IMIV_IMGUI_ROOT}/backends/imgui_impl_metal.mm")
+    list (APPEND _imiv_imgui_renderer_sources
+          "${OIIO_IMIV_IMGUI_ROOT}/backends/imgui_impl_metal.mm")
+elseif (_imiv_renderer_is_opengl)
+    list (APPEND _imiv_imgui_required_files
+          "${OIIO_IMIV_IMGUI_ROOT}/backends/imgui_impl_opengl3.h"
+          "${OIIO_IMIV_IMGUI_ROOT}/backends/imgui_impl_opengl3.cpp")
+    list (APPEND _imiv_imgui_renderer_sources
+          "${OIIO_IMIV_IMGUI_ROOT}/backends/imgui_impl_opengl3.cpp")
 endif ()
 set (_imiv_imgui_found ON)
 foreach (_imiv_required_file ${_imiv_imgui_required_files})
@@ -67,12 +123,10 @@ if (NOT _imiv_imgui_found)
 endif ()
 record_build_dependency (ImGui FOUND)
 
-set (_imiv_core_sources
+set (_imiv_shared_sources
      imiv_actions.cpp
      imiv_app.cpp
      imiv_aux_windows.cpp
-     imiv_capture.cpp
-     imiv_drag_drop.cpp
      imiv_file_dialog.cpp
      imiv_frame.cpp
      imiv_image_view.cpp
@@ -83,22 +137,51 @@ set (_imiv_core_sources
      imiv_renderer.cpp
      imiv_shader_compile.cpp
      imiv_style.cpp
+     imiv_upload_types.cpp
      imiv_ui.cpp
      imiv_viewer.cpp
+     imiv_main.cpp)
+
+set (_imiv_test_engine_integration_sources
+     imiv_test_engine.cpp)
+
+set (_imiv_platform_glfw_sources
+     imiv_drag_drop.cpp
+     imiv_platform_glfw.cpp)
+if (APPLE)
+    list (APPEND _imiv_platform_glfw_sources
+          external/dnd_glfw/dnd_glfw_macos.mm)
+endif ()
+
+set (_imiv_renderer_vulkan_sources
+     imiv_renderer_vulkan.cpp
+     imiv_capture.cpp
      imiv_vulkan_setup.cpp
      imiv_vulkan_ocio.cpp
      imiv_vulkan_preview.cpp
      imiv_vulkan_runtime.cpp
      imiv_vulkan_texture.cpp
-     imiv_vulkan_window.cpp
-     imiv_test_engine.cpp
-     imiv_main.cpp)
-
-if (APPLE)
-    list (APPEND _imiv_core_sources
-          external/dnd_glfw/dnd_glfw_macos.mm)
+     imiv_vulkan_window.cpp)
+
+set (_imiv_renderer_metal_sources
+     imiv_renderer_metal.mm)
+set (_imiv_renderer_opengl_sources
+     imiv_renderer_opengl.cpp)
+set (_imiv_renderer_selected_sources)
+if (_imiv_renderer_is_vulkan)
+    set (_imiv_renderer_selected_sources ${_imiv_renderer_vulkan_sources})
+elseif (_imiv_renderer_is_metal)
+    set (_imiv_renderer_selected_sources ${_imiv_renderer_metal_sources})
+elseif (_imiv_renderer_is_opengl)
+    set (_imiv_renderer_selected_sources ${_imiv_renderer_opengl_sources})
 endif ()
 
+set (_imiv_core_sources
+     ${_imiv_shared_sources}
+     ${_imiv_test_engine_integration_sources}
+     ${_imiv_platform_glfw_sources}
+     ${_imiv_renderer_selected_sources})
+
 set (_imiv_shader_src "${CMAKE_CURRENT_SOURCE_DIR}/shaders/imiv_upload_to_rgba.comp")
 set (_imiv_preview_vert_src "${CMAKE_CURRENT_SOURCE_DIR}/shaders/imiv_preview.vert")
 set (_imiv_preview_frag_src "${CMAKE_CURRENT_SOURCE_DIR}/shaders/imiv_preview.frag")
@@ -110,7 +193,7 @@ set (_imiv_preview_vert_spv "${CMAKE_CURRENT_BINARY_DIR}/imiv_preview.vert.spv")
 set (_imiv_preview_frag_spv "${CMAKE_CURRENT_BINARY_DIR}/imiv_preview.frag.spv")
 set (_imiv_shader_outputs)
 
-if (NOT APPLE)
+if (_imiv_renderer_is_vulkan)
     find_program (OIIO_IMIV_GLSLC_EXECUTABLE
                   NAMES glslc
                   HINTS
@@ -204,11 +287,8 @@ set (_imiv_imgui_sources
      "${OIIO_IMIV_IMGUI_ROOT}/imgui_draw.cpp"
      "${OIIO_IMIV_IMGUI_ROOT}/imgui_tables.cpp"
      "${OIIO_IMIV_IMGUI_ROOT}/imgui_widgets.cpp"
-     "${OIIO_IMIV_IMGUI_ROOT}/backends/imgui_impl_glfw.cpp")
-if (NOT APPLE)
-    list (APPEND _imiv_imgui_sources
-          "${OIIO_IMIV_IMGUI_ROOT}/backends/imgui_impl_vulkan.cpp")
-endif ()
+     "${OIIO_IMIV_IMGUI_ROOT}/backends/imgui_impl_glfw.cpp"
+     ${_imiv_imgui_renderer_sources})
 
 set (_imiv_test_engine_sources)
 set (_imiv_test_engine_dir "")
@@ -260,16 +340,16 @@ set (_imiv_link_libs
      OpenImageIO
      $<TARGET_NAME_IF_EXISTS:OpenColorIO::OpenColorIO>
      $<TARGET_NAME_IF_EXISTS:OpenColorIO::OpenColorIOHeaders>)
-if (NOT APPLE)
-    find_package (glfw3 CONFIG QUIET)
-    if (TARGET glfw)
-        list (APPEND _imiv_link_libs glfw)
-    else ()
-        message (STATUS
-                 "\n\n   WARNING: glfw not found -- 'imiv' will not be built!\n")
-        return ()
-    endif ()
+find_package (glfw3 CONFIG QUIET)
+if (TARGET glfw)
+    list (APPEND _imiv_link_libs glfw)
+else ()
+    message (STATUS
+             "\n\n   WARNING: glfw not found -- 'imiv' will not be built!\n")
+    return ()
+endif ()
 
+if (_imiv_renderer_is_vulkan)
     find_package (Vulkan QUIET)
     if (Vulkan_FOUND)
         record_build_dependency (Vulkan FOUND VERSION "${Vulkan_VERSION}")
@@ -513,12 +593,48 @@ if (NOT APPLE)
             GLSLANG_RUNTIME NOTFOUND
             NOT_FOUND_EXPLANATION "${_imiv_runtime_glslang_explanation}")
     endif ()
-else ()
+elseif (_imiv_renderer_is_metal)
     set (_imiv_has_runtime_glslang OFF)
     record_build_dependency (
         GLSLANG_RUNTIME NOTFOUND
         NOT_FOUND_EXPLANATION
             "(runtime shader compilation disabled on Metal backend)")
+    find_library (OIIO_IMIV_COCOA_FRAMEWORK Cocoa)
+    find_library (OIIO_IMIV_METAL_FRAMEWORK Metal)
+    find_library (OIIO_IMIV_QUARTZCORE_FRAMEWORK QuartzCore)
+    if (NOT OIIO_IMIV_COCOA_FRAMEWORK
+        OR NOT OIIO_IMIV_METAL_FRAMEWORK
+        OR NOT OIIO_IMIV_QUARTZCORE_FRAMEWORK)
+        message (STATUS
+                 "\n\n   WARNING: Metal frameworks not found -- 'imiv' will not be built!\n")
+        return ()
+    endif ()
+    list (APPEND _imiv_link_libs
+          ${OIIO_IMIV_COCOA_FRAMEWORK}
+          ${OIIO_IMIV_METAL_FRAMEWORK}
+          ${OIIO_IMIV_QUARTZCORE_FRAMEWORK})
+elseif (_imiv_renderer_is_opengl)
+    set (_imiv_has_runtime_glslang OFF)
+    record_build_dependency (
+        GLSLANG_RUNTIME NOTFOUND
+        NOT_FOUND_EXPLANATION
+            "(runtime shader compilation disabled on OpenGL backend)")
+    find_package (OpenGL QUIET)
+    if (TARGET OpenGL::GL)
+        list (APPEND _imiv_link_libs OpenGL::GL)
+    elseif (TARGET OpenGL::OpenGL)
+        list (APPEND _imiv_link_libs OpenGL::OpenGL)
+    else ()
+        message (STATUS
+                 "\n\n   WARNING: OpenGL not found -- 'imiv' will not be built!\n")
+        return ()
+    endif ()
+else ()
+    set (_imiv_has_runtime_glslang OFF)
+    record_build_dependency (
+        GLSLANG_RUNTIME NOTFOUND
+        NOT_FOUND_EXPLANATION
+            "(runtime shader compilation disabled on selected backend)")
 endif ()
 
 if (MSVC)
@@ -546,8 +662,17 @@ fancy_add_executable (
 source_group ("imgui" FILES ${_imiv_imgui_sources})
 source_group ("imgui_te" FILES
               ${_imiv_test_engine_sources}
-              "${CMAKE_CURRENT_SOURCE_DIR}/imiv_test_engine.cpp"
+              ${_imiv_test_engine_integration_sources}
               "${CMAKE_CURRENT_SOURCE_DIR}/imiv_test_engine.h")
+source_group ("imiv\\shared" FILES ${_imiv_shared_sources})
+source_group ("imiv\\platform\\glfw" FILES ${_imiv_platform_glfw_sources})
+source_group ("imiv\\renderer\\vulkan" FILES ${_imiv_renderer_vulkan_sources})
+if (_imiv_renderer_metal_sources)
+    source_group ("imiv\\renderer\\metal" FILES ${_imiv_renderer_metal_sources})
+endif ()
+if (_imiv_renderer_opengl_sources)
+    source_group ("imiv\\renderer\\opengl" FILES ${_imiv_renderer_opengl_sources})
+endif ()
 
 if (TARGET imiv)
     target_compile_definitions (imiv PRIVATE IMGUI_DISABLE_OBSOLETE_FUNCTIONS)
@@ -558,15 +683,16 @@ if (TARGET imiv)
     else ()
         target_compile_definitions (imiv PRIVATE IMIV_HAS_COMPUTE_UPLOAD_SHADERS=0)
     endif ()
-    if (APPLE)
-        target_compile_definitions (imiv PRIVATE IMIV_BACKEND_METAL_GLFW=1)
-        find_library (OIIO_IMIV_COCOA_FRAMEWORK Cocoa)
-        if (OIIO_IMIV_COCOA_FRAMEWORK)
-            target_link_libraries (imiv PRIVATE ${OIIO_IMIV_COCOA_FRAMEWORK})
-        endif ()
-    else ()
+    if (_imiv_renderer_is_vulkan)
         target_compile_definitions (imiv PRIVATE IMIV_BACKEND_VULKAN_GLFW=1
                                                   $<$<CONFIG:Debug>:IMIV_VULKAN_VALIDATION=1>)
+    elseif (_imiv_renderer_is_metal)
+        target_compile_definitions (imiv PRIVATE IMIV_BACKEND_METAL_GLFW=1)
+    elseif (_imiv_renderer_is_opengl)
+        target_compile_definitions (imiv PRIVATE IMIV_BACKEND_OPENGL_GLFW=1)
+        if (APPLE)
+            target_compile_definitions (imiv PRIVATE GL_SILENCE_DEPRECATION)
+        endif ()
     endif ()
     if (_imiv_has_runtime_glslang)
         target_compile_definitions (imiv PRIVATE IMIV_HAS_GLSLANG_RUNTIME=1)

src/imiv/imiv_actions.cpp

@@ -16,7 +16,8 @@
 #include <system_error>
 #include <vector>
 
-#if defined(IMIV_BACKEND_VULKAN_GLFW)
+#if defined(IMIV_BACKEND_VULKAN_GLFW) || defined(IMIV_BACKEND_METAL_GLFW) \
+    || defined(IMIV_BACKEND_OPENGL_GLFW)
 #    define GLFW_INCLUDE_NONE
 #    include <GLFW/glfw3.h>
 #endif
@@ -32,7 +33,6 @@ using namespace OIIO;
 
 namespace Imiv {
 
-#if defined(IMIV_BACKEND_VULKAN_GLFW)
 namespace {
 
     void clear_loaded_image_state(ViewerState& viewer)
@@ -98,11 +98,11 @@ namespace {
 
         std::tm local_tm      = {};
         const std::time_t now = std::time(nullptr);
-#    if defined(_WIN32)
+#if defined(_WIN32)
         localtime_s(&local_tm, &now);
-#    else
+#else
         localtime_r(&now, &local_tm);
-#    endif
+#endif
 
         char timestamp[64] = {};
         if (std::strftime(timestamp, sizeof(timestamp), "%Y%m%d_%H%M%S",
@@ -123,7 +123,6 @@ namespace {
     }
 
 }  // namespace
-#endif
 
 bool
 read_env_value(const char* name, std::string& out_value)
@@ -399,7 +398,6 @@ save_as_dialog_action(ViewerState& viewer)
     }
 }
 
-#if defined(IMIV_BACKEND_VULKAN_GLFW)
 void
 set_full_screen_mode(GLFWwindow* window, ViewerState& viewer, bool enable,
                      std::string& error_message)
@@ -679,9 +677,9 @@ close_current_image_action(RendererState& vk_state, ViewerState& viewer,
 {
     const std::string closing_path = viewer.image.path;
     const int closing_index        = viewer.current_path_index;
-#    if defined(IMIV_BACKEND_VULKAN_GLFW)
+#if defined(IMIV_BACKEND_VULKAN_GLFW)
     quiesce_viewer_texture_lifetime(vk_state, viewer.texture);
-#    endif
+#endif
     renderer_destroy_texture(vk_state, viewer.texture);
     remove_loaded_image_path(viewer, closing_path);
     if (!viewer.loaded_image_paths.empty()) {
@@ -847,8 +845,12 @@ capture_main_viewport_screenshot_action(RendererState& vk_state,
     out_path.clear();
     viewer.last_error.clear();
 
-    const int width  = std::max(0, vk_state.window_data.Width);
-    const int height = std::max(0, vk_state.window_data.Height);
+    int width  = std::max(0, vk_state.framebuffer_width);
+    int height = std::max(0, vk_state.framebuffer_height);
+#if defined(IMIV_BACKEND_VULKAN_GLFW)
+    width  = std::max(width, vk_state.window_data.Width);
+    height = std::max(height, vk_state.window_data.Height);
+#endif
     if (width <= 0 || height <= 0) {
         viewer.last_error = "screenshot failed: main viewport size is invalid";
         return false;
@@ -898,6 +900,4 @@ capture_main_viewport_screenshot_action(RendererState& vk_state,
     return true;
 }
 
-#endif
-
 }  // namespace Imiv