diff --git a/xo-imgui/CMakeLists.txt b/xo-imgui/CMakeLists.txt
index b182890d..6bfe8601 100644
--- a/xo-imgui/CMakeLists.txt
+++ b/xo-imgui/CMakeLists.txt
@@ -24,7 +24,7 @@ add_definitions(${PROJECT_CXX_FLAGS})
 
 set(XO_EXAMPLE_INSTALL_DIR bin/xo/imgui/example)
 
-#add_subdirectory(src/imgui)
+add_subdirectory(src/imgui)
 add_subdirectory(example)
 # add_subdirectory(utest)
 
diff --git a/xo-imgui/TROUBLESHOOTING b/xo-imgui/TROUBLESHOOTING
index fb848284..f0e2f0fd 100644
--- a/xo-imgui/TROUBLESHOOTING
+++ b/xo-imgui/TROUBLESHOOTING
@@ -2,7 +2,7 @@
 
    $ nixGL glxgears
 
-2. does vulkaninf work ?
+2. does vulkaninfo work ?
 
 
 For WSL2 (nvidia GPU)
diff --git a/xo-imgui/example/CMakeLists.txt b/xo-imgui/example/CMakeLists.txt
index ccde2610..830e824e 100644
--- a/xo-imgui/example/CMakeLists.txt
+++ b/xo-imgui/example/CMakeLists.txt
@@ -1,4 +1,4 @@
 add_subdirectory(ex1)
-#add_subdirectory(ex2)
-#add_subdirectory(ex3)
-#add_subdirectory(ex4)
+add_subdirectory(ex2)
+add_subdirectory(ex3)
+add_subdirectory(ex4)
diff --git a/xo-imgui/example/ex1/CMakeLists.txt b/xo-imgui/example/ex1/CMakeLists.txt
index 133a191e..768c94e3 100644
--- a/xo-imgui/example/ex1/CMakeLists.txt
+++ b/xo-imgui/example/ex1/CMakeLists.txt
@@ -3,7 +3,7 @@ if (XO_ENABLE_EXAMPLES)
 
     if (XO_ENABLE_OPENGL)
 
-        # TODO: maybe at some point incorporate imgui sources directly into xo source tree
+        # TODO: maybe incorporate imgui sources into xo-imgui library
         find_path(IMGUI_INCLUDE_DIR
             NAMES imgui/imgui.h
             DOC "path to imgui header"
diff --git a/xo-imgui/example/ex1/imgui_ex1.cpp b/xo-imgui/example/ex1/imgui_ex1.cpp
index f88fa789..c64de94b 100644
--- a/xo-imgui/example/ex1/imgui_ex1.cpp
+++ b/xo-imgui/example/ex1/imgui_ex1.cpp
@@ -26,7 +26,12 @@ int main(int, char **)
 
     std::cout << "Hello, world!" << std::endl;
 
-    SDL_SetHint(SDL_HINT_VIDEO_X11_FORCE_EGL, "1");
+    // 500fps with no hint
+    // 60gps with hint
+    //
+    // presumably GLX optimized relative to EGL
+
+    //SDL_SetHint(SDL_HINT_VIDEO_X11_FORCE_EGL, "1");
 
     SDL_Init(SDL_INIT_VIDEO);
 
diff --git a/xo-imgui/example/ex2/CMakeLists.txt b/xo-imgui/example/ex2/CMakeLists.txt
index 7a1f6265..df9e7cb9 100644
--- a/xo-imgui/example/ex2/CMakeLists.txt
+++ b/xo-imgui/example/ex2/CMakeLists.txt
@@ -1,66 +1,72 @@
 if (XO_ENABLE_EXAMPLES)
     # imgui dependency
 
-    find_path(IMGUI_INCLUDE_DIR
-        NAMES imgui/imgui.h
-        DOC "path to imgui header"
-    )
-    if (IMGUI_INCLUDE_DIR)
-        message(STATUS "found imgui/imgui.h in IMGUI_INCLUDE_DIR=[${IMGUI_INCLUDE_DIR}]")
-    else()
-        message(FATAL_ERROR "unable to find imgui.h")
+    if (XO_ENABLE_OPENGL)
+
+        find_path(IMGUI_INCLUDE_DIR
+            NAMES imgui/imgui.h
+            DOC "path to imgui header"
+            HINTS ${PROJECT_SOURCE_DIR}/include
+        )
+        if (IMGUI_INCLUDE_DIR)
+            message(STATUS "found imgui/imgui.h in IMGUI_INCLUDE_DIR=[${IMGUI_INCLUDE_DIR}]")
+        else()
+            message(FATAL_ERROR "unable to find imgui.h")
+        endif()
+
+        # target executable
+
+        set(SELF_EXE imgui_ex2)
+        add_executable(${SELF_EXE} imgui_ex2.cpp
+                    ${IMGUI_INCLUDE_DIR}/imgui/imgui.cpp
+                    ${IMGUI_INCLUDE_DIR}/imgui/imgui_demo.cpp
+                    ${IMGUI_INCLUDE_DIR}/imgui/imgui_draw.cpp
+                    ${IMGUI_INCLUDE_DIR}/imgui/imgui_widgets.cpp
+                    ${IMGUI_INCLUDE_DIR}/imgui/imgui_tables.cpp
+                    ${IMGUI_INCLUDE_DIR}/imgui/backends/imgui_impl_sdl2.cpp
+                    ${IMGUI_INCLUDE_DIR}/imgui/backends/imgui_impl_opengl3.cpp
+                    #${IMGUI_INCLUDE_DIR}/imgui/backends/imgui_impl_vulkan.cpp
+        )
+        xo_include_options2(${SELF_EXE})
+
+        # OpenGL dependency
+
+        # have to choose between
+        #   libGL.so
+        # or
+        #   libOpenGL.so + libGLX.so    # GLVND = OpenGL Vendor Neutral Dispatch (e.g. mesa|nvda)
+        #
+        # expect in .build/CMakeCache.txt:
+        #   OPENGL_opengl_LIBRARY:FILEPATH=/path/to/libOpenGL.so
+        #   OpenGL_DIR:PATH=OpenGL_DIR-NOTFOUND  # no cmake config file
+
+        #    set(OpenGL_GL_PREFERENCE GLVND)  # or LEGACY
+        find_package(OpenGL REQUIRED)  # find_package(OpenGL CONFIG REQUIRE) won't work
+        target_link_libraries(${SELF_EXE} PUBLIC OpenGL::GL)
+
+        #    find_package(Vulkan REQUIRED)
+        #    target_link_libraries(${SELF_EXE} PUBLIC Vulkan::Vulkan)
+
+        # GLEW dependency
+        xo_external_pkgconfig_dependency(${SELF_EXE} GLEW glew)
+
+        # GLFW dependency
+        #    find_package(glfw3 CONFIG REQUIRED)
+        #    target_link_libraries(${SELF_EXE} PUBLIC glfw) # want -lglfw
+
+        # SDL2 dependency
+        xo_external_pkgconfig_dependency(${SELF_EXE} SDL2 sdl2)
+
+        # would prefer to use just IMGUI_INCLUDE_DIR,
+        # but imgui/backends/ .h files don't quote the imgui/ stem
+        #
+        target_include_directories(${SELF_EXE} PUBLIC ${IMGUI_INCLUDE_DIR}/imgui)
+
+        xo_dependency(${SELF_EXE} xo_object)
+        xo_dependency(${SELF_EXE} randomgen)
+        xo_dependency(${SELF_EXE} xo_flatstring)
+        xo_dependency(${SELF_EXE} xo_alloc)
+
+        install(TARGETS ${SELF_EXE} DESTINATION ${XO_EXAMPLE_INSTALL_DIR})
     endif()
-
-    # target executable
-
-    set(SELF_EXE imgui_ex2)
-    add_executable(${SELF_EXE} imgui_ex2.cpp
-        ${IMGUI_INCLUDE_DIR}/imgui/imgui.cpp
-        ${IMGUI_INCLUDE_DIR}/imgui/imgui_demo.cpp
-        ${IMGUI_INCLUDE_DIR}/imgui/imgui_draw.cpp
-        ${IMGUI_INCLUDE_DIR}/imgui/imgui_widgets.cpp
-        ${IMGUI_INCLUDE_DIR}/imgui/imgui_tables.cpp
-        ${IMGUI_INCLUDE_DIR}/imgui/backends/imgui_impl_sdl2.cpp
-        ${IMGUI_INCLUDE_DIR}/imgui/backends/imgui_impl_opengl3.cpp
-        #${IMGUI_INCLUDE_DIR}/imgui/backends/imgui_impl_vulkan.cpp
-    )
-    xo_include_options2(${SELF_EXE})
-
-    # OpenGL dependency
-
-    # have to choose between
-    #   libGL.so
-    # or
-    #   libOpenGL.so + libGLX.so    # GLVND = OpenGL Vendor Neutral Dispatch (e.g. mesa|nvda)
-    #
-    # expect in .build/CMakeCache.txt:
-    #   OPENGL_opengl_LIBRARY:FILEPATH=/path/to/libOpenGL.so
-    #   OpenGL_DIR:PATH=OpenGL_DIR-NOTFOUND  # no cmake config file
-
-#    set(OpenGL_GL_PREFERENCE GLVND)  # or LEGACY
-    find_package(OpenGL REQUIRED)  # find_package(OpenGL CONFIG REQUIRE) won't work
-    target_link_libraries(${SELF_EXE} PUBLIC OpenGL::GL)
-
-#    find_package(Vulkan REQUIRED)
-#    target_link_libraries(${SELF_EXE} PUBLIC Vulkan::Vulkan)
-
-    # GLEW dependency
-    xo_external_pkgconfig_dependency(${SELF_EXE} GLEW glew)
-
-    # GLFW dependency
-#    find_package(glfw3 CONFIG REQUIRED)
-#    target_link_libraries(${SELF_EXE} PUBLIC glfw) # want -lglfw
-
-    # SDL2 dependency
-    xo_external_pkgconfig_dependency(${SELF_EXE} SDL2 sdl2)
-
-    # would prefer to use just IMGUI_INCLUDE_DIR,
-    # but imgui/backends/ .h files don't quote the imgui/ stem
-    #
-    target_include_directories(${SELF_EXE} PUBLIC ${IMGUI_INCLUDE_DIR}/imgui)
-
-    xo_dependency(${SELF_EXE} xo_object)
-    xo_dependency(${SELF_EXE} randomgen)
-    xo_dependency(${SELF_EXE} xo_flatstring)
-    xo_dependency(${SELF_EXE} xo_alloc)
 endif()
diff --git a/xo-imgui/example/ex2/imgui_ex2.cpp b/xo-imgui/example/ex2/imgui_ex2.cpp
index 51b0dbb4..0b5aff1a 100644
--- a/xo-imgui/example/ex2/imgui_ex2.cpp
+++ b/xo-imgui/example/ex2/imgui_ex2.cpp
@@ -884,7 +884,7 @@ write_gc_history_tooltip(gc_history_headline headline,
 {
     xo::flatstring<512> retval;
 
-    xo::flatstring<512> headline_str;
+    xo::flatstring<256> headline_str;
     switch (headline) {
     case gc_history_headline::survive:
         snprintf(headline_str.data(), headline_str.capacity(),
@@ -921,10 +921,8 @@ write_gc_history_tooltip(gc_history_headline headline,
         break;
     }
 
-
-
     snprintf(retval.data(), retval.capacity(),
-             "%s\n"
+             "%.*s\n"
              "\n"
              " gcseq: %lu\n"
              " type: %s\n"
@@ -937,7 +935,7 @@ write_gc_history_tooltip(gc_history_headline headline,
              " garbage\u2099: %lu\n" /*garbageN*/
              " effort: %lu dt: %.1lfus\n"
              " copy efficiency: %.1lf%% collection rate: %.0lf bytes/sec",
-             headline_str.c_str(),
+             static_cast<int>(headline_str.capacity()), headline_str.c_str(),
              stats.gc_seq_,
              (stats.upto_ == generation::nursery) ? "incremental" : "FULL",
              stats.new_alloc_z_,
diff --git a/xo-imgui/example/ex3/CMakeLists.txt b/xo-imgui/example/ex3/CMakeLists.txt
index c291476f..4c55b0e3 100644
--- a/xo-imgui/example/ex3/CMakeLists.txt
+++ b/xo-imgui/example/ex3/CMakeLists.txt
@@ -1,67 +1,74 @@
 if (XO_ENABLE_EXAMPLES)
     # imgui dependency
 
-    find_path(IMGUI_INCLUDE_DIR
-        NAMES imgui/imgui.h
-        DOC "path to imgui header"
-    )
-    if (IMGUI_INCLUDE_DIR)
-        message(STATUS "found imgui/imgui.h in IMGUI_INCLUDE_DIR=[${IMGUI_INCLUDE_DIR}]")
-    else()
-        message(FATAL_ERROR "unable to find imgui.h")
+    if (XO_ENABLE_VULKAN)
+
+        find_path(
+            IMGUI_INCLUDE_DIR
+            NAMES imgui/imgui.h
+            DOC "path to imgui header"
+            HINTS ${PROJECT_SOURCE_DIR}/include
+        )
+        if (IMGUI_INCLUDE_DIR)
+            message(STATUS "found imgui/imgui.h in IMGUI_INCLUDE_DIR=[${IMGUI_INCLUDE_DIR}]")
+        else()
+            message(FATAL_ERROR "unable to find imgui.h")
+        endif()
+
+        # target executable
+
+        set(SELF_EXE imgui_ex3)
+        add_executable(${SELF_EXE} imgui_ex3.cpp
+                    ${IMGUI_INCLUDE_DIR}/imgui/imgui.cpp
+                    ${IMGUI_INCLUDE_DIR}/imgui/imgui_demo.cpp
+                    ${IMGUI_INCLUDE_DIR}/imgui/imgui_draw.cpp
+                    ${IMGUI_INCLUDE_DIR}/imgui/imgui_widgets.cpp
+                    ${IMGUI_INCLUDE_DIR}/imgui/imgui_tables.cpp
+                    ${IMGUI_INCLUDE_DIR}/imgui/backends/imgui_impl_sdl2.cpp
+                    #${IMGUI_INCLUDE_DIR}/imgui/backends/imgui_impl_opengl3.cpp
+                    #${IMGUI_INCLUDE_DIR}/imgui/backends/imgui_impl_glfw.cpp
+                    ${IMGUI_INCLUDE_DIR}/imgui/backends/imgui_impl_vulkan.cpp
+        )
+        xo_include_options2(${SELF_EXE})
+
+        # OpenGL dependency
+
+        # have to choose between
+        #   libGL.so
+        # or
+        #   libOpenGL.so + libGLX.so    # GLVND = OpenGL Vendor Neutral Dispatch (e.g. mesa|nvda)
+        #
+        # expect in .build/CMakeCache.txt:
+        #   OPENGL_opengl_LIBRARY:FILEPATH=/path/to/libOpenGL.so
+        #   OpenGL_DIR:PATH=OpenGL_DIR-NOTFOUND  # no cmake config file
+
+        #    set(OpenGL_GL_PREFERENCE GLVND)  # or LEGACY
+        #    find_package(OpenGL REQUIRED)  # find_package(OpenGL CONFIG REQUIRE) won't work
+        #    target_link_libraries(${SELF_EXE} PUBLIC OpenGL::GL)
+
+        find_package(Vulkan REQUIRED)
+        target_link_libraries(${SELF_EXE} PUBLIC Vulkan::Vulkan)
+
+        # GLEW dependency
+        xo_external_pkgconfig_dependency(${SELF_EXE} GLEW glew)
+
+        # GLFW dependency
+        #find_package(glfw3 CONFIG REQUIRED)
+        #target_link_libraries(${SELF_EXE} PUBLIC glfw) # want -lglfw
+
+        # SDL2 dependency
+        xo_external_pkgconfig_dependency(${SELF_EXE} SDL2 sdl2)
+
+        # would prefer to use just IMGUI_INCLUDE_DIR,
+        # but imgui/backends/ .h files don't quote the imgui/ stem
+        #
+        target_include_directories(${SELF_EXE} PUBLIC ${IMGUI_INCLUDE_DIR}/imgui)
+
+        xo_dependency(${SELF_EXE} xo_object)
+        xo_dependency(${SELF_EXE} randomgen)
+        xo_dependency(${SELF_EXE} xo_flatstring)
+        xo_dependency(${SELF_EXE} xo_alloc)
+
+        install(TARGETS ${SELF_EXE} DESTINATION ${XO_EXAMPLE_INSTALL_DIR})
     endif()
-
-    # target executable
-
-    set(SELF_EXE imgui_ex3)
-    add_executable(${SELF_EXE} imgui_ex3.cpp
-        ${IMGUI_INCLUDE_DIR}/imgui/imgui.cpp
-        ${IMGUI_INCLUDE_DIR}/imgui/imgui_demo.cpp
-        ${IMGUI_INCLUDE_DIR}/imgui/imgui_draw.cpp
-        ${IMGUI_INCLUDE_DIR}/imgui/imgui_widgets.cpp
-        ${IMGUI_INCLUDE_DIR}/imgui/imgui_tables.cpp
-        ${IMGUI_INCLUDE_DIR}/imgui/backends/imgui_impl_sdl2.cpp
-        #${IMGUI_INCLUDE_DIR}/imgui/backends/imgui_impl_opengl3.cpp
-        #${IMGUI_INCLUDE_DIR}/imgui/backends/imgui_impl_glfw.cpp
-        ${IMGUI_INCLUDE_DIR}/imgui/backends/imgui_impl_vulkan.cpp
-    )
-    xo_include_options2(${SELF_EXE})
-
-    # OpenGL dependency
-
-    # have to choose between
-    #   libGL.so
-    # or
-    #   libOpenGL.so + libGLX.so    # GLVND = OpenGL Vendor Neutral Dispatch (e.g. mesa|nvda)
-    #
-    # expect in .build/CMakeCache.txt:
-    #   OPENGL_opengl_LIBRARY:FILEPATH=/path/to/libOpenGL.so
-    #   OpenGL_DIR:PATH=OpenGL_DIR-NOTFOUND  # no cmake config file
-
-#    set(OpenGL_GL_PREFERENCE GLVND)  # or LEGACY
-#    find_package(OpenGL REQUIRED)  # find_package(OpenGL CONFIG REQUIRE) won't work
-#    target_link_libraries(${SELF_EXE} PUBLIC OpenGL::GL)
-
-    find_package(Vulkan REQUIRED)
-    target_link_libraries(${SELF_EXE} PUBLIC Vulkan::Vulkan)
-
-    # GLEW dependency
-    xo_external_pkgconfig_dependency(${SELF_EXE} GLEW glew)
-
-    # GLFW dependency
-    #find_package(glfw3 CONFIG REQUIRED)
-    #target_link_libraries(${SELF_EXE} PUBLIC glfw) # want -lglfw
-
-    # SDL2 dependency
-    xo_external_pkgconfig_dependency(${SELF_EXE} SDL2 sdl2)
-
-    # would prefer to use just IMGUI_INCLUDE_DIR,
-    # but imgui/backends/ .h files don't quote the imgui/ stem
-    #
-    target_include_directories(${SELF_EXE} PUBLIC ${IMGUI_INCLUDE_DIR}/imgui)
-
-    xo_dependency(${SELF_EXE} xo_object)
-    xo_dependency(${SELF_EXE} randomgen)
-    xo_dependency(${SELF_EXE} xo_flatstring)
-    xo_dependency(${SELF_EXE} xo_alloc)
 endif()
diff --git a/xo-imgui/example/ex3/imgui_ex3.cpp b/xo-imgui/example/ex3/imgui_ex3.cpp
index 0ca0be17..acd89fcf 100644
--- a/xo-imgui/example/ex3/imgui_ex3.cpp
+++ b/xo-imgui/example/ex3/imgui_ex3.cpp
@@ -4365,17 +4365,23 @@ private:
             throw std::runtime_error("Failed to get SDL Vulkan extensions!");
         }
 
+#ifdef __apple__
         // Add portability extension for MoltenVK (macOS)
         extensions.push_back(VK_KHR_PORTABILITY_ENUMERATION_EXTENSION_NAME);
+#endif
 
         createInfo.enabledExtensionCount = extensions.size();
         createInfo.ppEnabledExtensionNames = extensions.data();
         createInfo.enabledLayerCount = 0;
 
+#ifdef __apple__
         // CRITICAL: Enable portability enumeration flag for MoltenVK
         createInfo.flags |= VK_INSTANCE_CREATE_ENUMERATE_PORTABILITY_BIT_KHR;
+#endif
 
-        if (vkCreateInstance(&createInfo, nullptr, &instance) != VK_SUCCESS) {
+        int result = vkCreateInstance(&createInfo, nullptr, &instance);
+        if (result != VK_SUCCESS) {
+            printf("vkCreateInstance failed with error: %d\n", result);
             throw std::runtime_error("Failed to create instance!");
         }
     }
diff --git a/xo-imgui/example/ex4/CMakeLists.txt b/xo-imgui/example/ex4/CMakeLists.txt
index bdd8e7fc..4bc2353d 100644
--- a/xo-imgui/example/ex4/CMakeLists.txt
+++ b/xo-imgui/example/ex4/CMakeLists.txt
@@ -1,18 +1,5 @@
 if (XO_ENABLE_EXAMPLES)
-    # imgui dependency
-
-    find_path(IMGUI_INCLUDE_DIR
-        NAMES imgui/imgui.h
-        DOC "path to imgui header"
-    )
-    if (IMGUI_INCLUDE_DIR)
-        message(STATUS "found imgui/imgui.h in IMGUI_INCLUDE_DIR=[${IMGUI_INCLUDE_DIR}]")
-    else()
-        message(FATAL_ERROR "unable to find imgui.h")
-    endif()
-
     # target executable
-
     set(SELF_EXE imgui_ex4)
     add_executable(${SELF_EXE} imgui_ex4.cpp
         AppState.cpp
@@ -20,54 +7,13 @@ if (XO_ENABLE_EXAMPLES)
         GcStateDescription.cpp
         AnimateGcCopyCb.cpp
         GenerationLayout.cpp
-#        ${IMGUI_INCLUDE_DIR}/imgui/imgui.cpp
-#        ${IMGUI_INCLUDE_DIR}/imgui/imgui_demo.cpp
-#        ${IMGUI_INCLUDE_DIR}/imgui/imgui_draw.cpp
-#        ${IMGUI_INCLUDE_DIR}/imgui/imgui_widgets.cpp
-#        ${IMGUI_INCLUDE_DIR}/imgui/imgui_tables.cpp
-#        ${IMGUI_INCLUDE_DIR}/imgui/backends/imgui_impl_sdl2.cpp
-        #${IMGUI_INCLUDE_DIR}/imgui/backends/imgui_impl_opengl3.cpp
-        #${IMGUI_INCLUDE_DIR}/imgui/backends/imgui_impl_glfw.cpp
-#        ${IMGUI_INCLUDE_DIR}/imgui/backends/imgui_impl_vulkan.cpp
     )
     xo_include_options2(${SELF_EXE})
 
-    # OpenGL dependency
-
-    # have to choose between
-    #   libGL.so
-    # or
-    #   libOpenGL.so + libGLX.so    # GLVND = OpenGL Vendor Neutral Dispatch (e.g. mesa|nvda)
-    #
-    # expect in .build/CMakeCache.txt:
-    #   OPENGL_opengl_LIBRARY:FILEPATH=/path/to/libOpenGL.so
-    #   OpenGL_DIR:PATH=OpenGL_DIR-NOTFOUND  # no cmake config file
-
-#    set(OpenGL_GL_PREFERENCE GLVND)  # or LEGACY
-#    find_package(OpenGL REQUIRED)  # find_package(OpenGL CONFIG REQUIRE) won't work
-#    target_link_libraries(${SELF_EXE} PUBLIC OpenGL::GL)
-
-    find_package(Vulkan REQUIRED)
-    target_link_libraries(${SELF_EXE} PUBLIC Vulkan::Vulkan)
-
-    # GLEW dependency
-    xo_external_pkgconfig_dependency(${SELF_EXE} GLEW glew)
-
-    # GLFW dependency
-    #find_package(glfw3 CONFIG REQUIRED)
-    #target_link_libraries(${SELF_EXE} PUBLIC glfw) # want -lglfw
-
-    # SDL2 dependency
-    xo_external_pkgconfig_dependency(${SELF_EXE} SDL2 sdl2)
-
-    # would prefer to use just IMGUI_INCLUDE_DIR,
-    # but imgui/backends/ .h files don't quote the imgui/ stem
-    #
-    target_include_directories(${SELF_EXE} PUBLIC ${IMGUI_INCLUDE_DIR}/imgui)
-
     xo_self_dependency(${SELF_EXE} xo_imgui)
     xo_dependency(${SELF_EXE} xo_object)
     xo_dependency(${SELF_EXE} randomgen)
     xo_dependency(${SELF_EXE} xo_flatstring)
     xo_dependency(${SELF_EXE} xo_alloc)
+    xo_dependency(${SELF_EXE} indentlog)
 endif()
diff --git a/xo-imgui/example/ex4/DrawState.cpp b/xo-imgui/example/ex4/DrawState.cpp
index f5cc9dea..fa68af10 100644
--- a/xo-imgui/example/ex4/DrawState.cpp
+++ b/xo-imgui/example/ex4/DrawState.cpp
@@ -251,7 +251,7 @@ DrawState::write_gc_history_tooltip(gc_history_headline headline,
 {
     xo::flatstring<512> retval;
 
-    xo::flatstring<512> headline_str;
+    xo::flatstring<256> headline_str;
     switch (headline) {
     case gc_history_headline::survive:
         snprintf(headline_str.data(), headline_str.capacity(),
@@ -288,10 +288,8 @@ DrawState::write_gc_history_tooltip(gc_history_headline headline,
         break;
     }
 
-
-
     snprintf(retval.data(), retval.capacity(),
-             "%s\n"
+             "%.*s\n"
              "\n"
              " gcseq: %lu\n"
              " type: %s\n"
@@ -304,7 +302,7 @@ DrawState::write_gc_history_tooltip(gc_history_headline headline,
              " garbage\u2099: %lu\n" /*garbageN*/
              " effort: %lu dt: %.1lfus\n"
              " copy efficiency: %.1lf%% collection rate: %.0lf bytes/sec",
-             headline_str.c_str(),
+             static_cast<int>(headline_str.capacity()), headline_str.c_str(),
              stats.gc_seq_,
              (stats.upto_ == generation::nursery) ? "incremental" : "FULL",
              stats.new_alloc_z_,
diff --git a/xo-imgui/example/ex4/GenerationLayout.hpp b/xo-imgui/example/ex4/GenerationLayout.hpp
index 2d338aa1..78cc46a5 100644
--- a/xo-imgui/example/ex4/GenerationLayout.hpp
+++ b/xo-imgui/example/ex4/GenerationLayout.hpp
@@ -1,5 +1,7 @@
 /* GenerationLayout.hpp */
 
+#pragma once
+
 #include "GcGenerationDescription.hpp"
 #include "xo/imgui/ImRect.hpp"
 
@@ -90,4 +92,5 @@ struct GenerationLayout {
     ImRect mem_rect_to_;
 };
 
+
 /* GenerationLayout.hpp */
diff --git a/xo-imgui/example/ex4/imgui_ex4.cpp b/xo-imgui/example/ex4/imgui_ex4.cpp
index d70e7c4a..ed2fdfbd 100644
--- a/xo-imgui/example/ex4/imgui_ex4.cpp
+++ b/xo-imgui/example/ex4/imgui_ex4.cpp
@@ -1,11 +1,16 @@
 /* imgui_ex4.cpp */
 
 #include "xo/imgui/VulkanApp.hpp"
+#ifdef TEMPORARILY_REMOVE
 #include "xo/imgui/ImRect.hpp"
+#endif
 #include "AppState.hpp"
 #include "DrawState.hpp"
 #include <backends/imgui_impl_sdl2.h>
 #include <backends/imgui_impl_vulkan.h>
+
+#include "xo/indentlog/scope.hpp"
+
 #include <iostream>
 #include <fstream>
 
@@ -14,6 +19,7 @@ namespace {
     using xo::scope;
     using xo::xtag;
 
+
     void
     app_duty_cycle_top(AppState * p_app_state,
                        DrawState * p_draw_state)
@@ -173,6 +179,11 @@ namespace {
 }
 
 int main() {
+    printf("Hello world\n");
+
+    scope log(XO_DEBUG(true));
+    log && log("starting main");
+
     AppState app_state;
     DrawState draw_state;
     draw_state.gcstate_ = app_state.snapshot_gc_state();
diff --git a/xo-imgui/src/imgui/CMakeLists.txt b/xo-imgui/src/imgui/CMakeLists.txt
index 7a4670e5..36663057 100644
--- a/xo-imgui/src/imgui/CMakeLists.txt
+++ b/xo-imgui/src/imgui/CMakeLists.txt
@@ -2,7 +2,9 @@
 
 find_path(IMGUI_INCLUDE_DIR
     NAMES imgui/imgui.h
-    DOC "path to imgui header")
+    DOC "path to imgui header"
+    HINTS ${PROJECT_SOURCE_DIR}/include
+)
 if (IMGUI_INCLUDE_DIR)
     message(STATUS
         "found imgui/imgui.h in IMGUI_INCLUDE_DIR=[${IMGUI_INCLUDE_DIR}]")
@@ -10,10 +12,11 @@ else()
     message(FATAL_ERROR "unable to find imgui.h")
 endif()
 
-set(SELF_LIB xo_imgui)
-set(SELF_SRCS
-    VulkanApp.cpp
-    ImRect.cpp
+if (XO_ENABLE_VULKAN)
+    set(SELF_LIB xo_imgui)
+    set(SELF_SRCS
+        VulkanApp.cpp
+        ImRect.cpp
         ${IMGUI_INCLUDE_DIR}/imgui/imgui.cpp
         ${IMGUI_INCLUDE_DIR}/imgui/imgui_demo.cpp
         ${IMGUI_INCLUDE_DIR}/imgui/imgui_draw.cpp
@@ -22,21 +25,23 @@ set(SELF_SRCS
         ${IMGUI_INCLUDE_DIR}/imgui/backends/imgui_impl_sdl2.cpp
         #${IMGUI_INCLUDE_DIR}/imgui/backends/imgui_impl_opengl3.cpp
         #${IMGUI_INCLUDE_DIR}/imgui/backends/imgui_impl_glfw.cpp
-        ${IMGUI_INCLUDE_DIR}/imgui/backends/imgui_impl_vulkan.cpp)
+        ${IMGUI_INCLUDE_DIR}/imgui/backends/imgui_impl_vulkan.cpp
+    )
 
-xo_add_shared_library4(
-    ${SELF_LIB}
-    ${PROJECT_NAME}Targets ${PROJECT_VERSION} 1 ${SELF_SRCS}
-)
+    xo_add_shared_library4(
+        ${SELF_LIB}
+        ${PROJECT_NAME}Targets ${PROJECT_VERSION} 1 ${SELF_SRCS}
+    )
 
-find_package(Vulkan REQUIRED)
-target_link_libraries(${SELF_LIB} PUBLIC Vulkan::Vulkan)
+    find_package(Vulkan REQUIRED)
+    target_link_libraries(${SELF_LIB} PUBLIC Vulkan::Vulkan)
 
-xo_external_pkgconfig_dependency(${SELF_LIB} SDL2 sdl2)
+    xo_external_pkgconfig_dependency(${SELF_LIB} SDL2 sdl2)
 
-# NOTE: would prefer to use just IMGUI_INCLUDE_DIR,
-# but imgui/backends/ .h files don't quote the imgui/ stem
-#
-target_include_directories(${SELF_LIB} PUBLIC ${IMGUI_INCLUDE_DIR}/imgui)
+    # NOTE: would prefer to use just IMGUI_INCLUDE_DIR,
+    # but imgui/backends/ .h files don't quote the imgui/ stem
+    #
+    target_include_directories(${SELF_LIB} PUBLIC ${IMGUI_INCLUDE_DIR}/imgui)
 
-xo_dependency(${SELF_LIB} indentlog)
+    xo_dependency(${SELF_LIB} indentlog)
+endif()
diff --git a/xo-imgui/src/imgui/VulkanApp.cpp b/xo-imgui/src/imgui/VulkanApp.cpp
index 430a1585..28b70350 100644
--- a/xo-imgui/src/imgui/VulkanApp.cpp
+++ b/xo-imgui/src/imgui/VulkanApp.cpp
@@ -6,6 +6,10 @@
 #include <backends/imgui_impl_sdl2.h>
 #include <backends/imgui_impl_vulkan.h>
 #include <cstdint>
+#include <vulkan/vulkan_core.h>
+#ifdef __linux__
+# include <vulkan/vulkan_wayland.h>
+#endif
 
 using xo::scope;
 using xo::xtag;
@@ -38,6 +42,12 @@ VulkanApp::run() {
 
 void
 VulkanApp::init_window() {
+#ifdef __linux__
+    // on linux (at least for wsl2) force x11 with xlib instead of xcb
+    // alternatively could set env var SDL_VIDEODRIVER
+    SDL_SetHint(SDL_HINT_VIDEODRIVER, "x11");
+#endif
+
     if (SDL_Init(SDL_INIT_VIDEO) != 0) {
         throw std::runtime_error("Failed to initialize SDL!");
     }
@@ -97,8 +107,21 @@ VulkanApp::create_instance()
         throw std::runtime_error("Failed to get SDL Vulkan extensions!");
     }
 
+#ifdef __APPLE__
     // Add portability extension for MoltenVK (macOS)
     extensions.push_back(VK_KHR_PORTABILITY_ENUMERATION_EXTENSION_NAME);
+    // claude.ai says:
+    //  extensions.push_back("VK_KHR_get_physical_device_properties2")
+#endif
+
+#ifdef __linux__
+    extensions.push_back(VK_KHR_SURFACE_EXTENSION_NAME);
+    // native wayland drivers.  or use VK_KHR_XLIB_SURFACE_EXTENSION_NAME here
+    //extensions.push_back(VK_KHR_XLIB_SURFACE_EXTENSION_NAME);
+    //extensions.push_back(VK_KHR_WAYLAND_SURFACE_EXTENSION_NAME);
+#endif
+
+    extensions.push_back(VK_EXT_DEBUG_UTILS_EXTENSION_NAME);
 
     createInfo.enabledExtensionCount = extensions.size();
     createInfo.ppEnabledExtensionNames = extensions.data();