Backends: Vulkan: Add viewports desired present mode (at init)

- Add `ImGui_ImplVulkan_SelectPresentMode(ImGuiViewport*)` for later re-use

Author: SuperRonan

backends/imgui_impl_vulkan.cpp

@@ -1960,6 +1960,26 @@ ImGui_ImplVulkanH_Window* ImGui_ImplVulkanH_GetWindowDataFromViewport(ImGuiViewp
 // If you are new to dear imgui or creating a new binding for dear imgui, it is recommended that you completely ignore this section first..
 //--------------------------------------------------------------------------------------------------------
 
+static void ImGui_ImplVulkan_SelectPresentMode(ImGuiViewport* viewport)
+{
+    ImGui_ImplVulkan_Data* bd = ImGui_ImplVulkan_GetBackendData();
+    ImGui_ImplVulkan_InitInfo* v = &bd->VulkanInitInfo;
+    ImGui_ImplVulkan_ViewportData* vd = (ImGui_ImplVulkan_ViewportData*)viewport->RendererUserData;
+    ImGui_ImplVulkanH_Window* wd = &vd->Window;
+
+    // FIXME-VULKAN: Even thought mailbox seems to get us maximum framerate with a single window, it halves framerate with a second window etc. (w/ Nvidia and SDK 1.82.1)
+    const VkPresentModeKHR presentModes[] = { v->SecondaryViewportsInfo.DesiredPresentMode, VK_PRESENT_MODE_MAILBOX_KHR, VK_PRESENT_MODE_IMMEDIATE_KHR, VK_PRESENT_MODE_FIFO_KHR };
+    int presentModesCount = IM_ARRAYSIZE(presentModes);
+    const VkPresentModeKHR* pPresentModes = presentModes;
+    if (pPresentModes[0] == VK_PRESENT_MODE_MAX_ENUM_KHR)
+    {
+        ++pPresentModes;
+        --presentModesCount;
+    }
+    wd->PresentMode = ImGui_ImplVulkanH_SelectPresentMode(v->PhysicalDevice, wd->Surface, presentModes, presentModesCount);
+    //printf("[vulkan] Secondary window selected PresentMode = %d\n", wd->PresentMode);
+}
+
 static void ImGui_ImplVulkan_CreateWindow(ImGuiViewport* viewport)
 {
     ImGui_ImplVulkan_Data* bd = ImGui_ImplVulkan_GetBackendData();
@@ -1997,10 +2017,7 @@ static void ImGui_ImplVulkan_CreateWindow(ImGuiViewport* viewport)
     wd->SurfaceFormat = ImGui_ImplVulkanH_SelectSurfaceFormat(v->PhysicalDevice, wd->Surface, pRequestSurfaceImageFormats, requestSurfaceImageFormatsCount, requestSurfaceColorSpace);
 
     // Select Present Mode
-    // FIXME-VULKAN: Even thought mailbox seems to get us maximum framerate with a single window, it halves framerate with a second window etc. (w/ Nvidia and SDK 1.82.1)
-    VkPresentModeKHR present_modes[] = { VK_PRESENT_MODE_MAILBOX_KHR, VK_PRESENT_MODE_IMMEDIATE_KHR, VK_PRESENT_MODE_FIFO_KHR };
-    wd->PresentMode = ImGui_ImplVulkanH_SelectPresentMode(v->PhysicalDevice, wd->Surface, &present_modes[0], IM_ARRAYSIZE(present_modes));
-    //printf("[vulkan] Secondary window selected PresentMode = %d\n", wd->PresentMode);
+    ImGui_ImplVulkan_SelectPresentMode(viewport);
 
     // Create SwapChain, RenderPass, Framebuffer, etc.
     wd->ClearEnable = (viewport->Flags & ImGuiViewportFlags_NoRendererClear) ? false : true;

backends/imgui_impl_vulkan.h

@@ -84,6 +84,9 @@ struct ImGui_ImplVulkan_SecondaryViewportsInfo
 {
     // Ignored if .format == VK_FORMAT_UNDEFINED
     VkSurfaceFormatKHR              DesiredFormat;
+    // Ignored if set to VK_PRESENT_MODE_MAX_ENUM_KHR
+    // Warning: The default zero initialized value is VK_PRESENT_MODE_IMMEDIATE_KHR!
+    VkPresentModeKHR                DesiredPresentMode;
 
     VkImageUsageFlags               SwapChainImageUsage;            // Extra flags for vkCreateSwapchainKHR() calls for secondary viewports. We automatically add VK_IMAGE_USAGE_COLOR_ATTACHMENT_BIT. You can add e.g. VK_IMAGE_USAGE_TRANSFER_SRC_BIT if you need to capture from viewports.
 };