[wpigui] Limit frame rate to 120 fps by default (#5030)

Limiting with vsync is apparently unreliable on a number of systems;
this resulted in high CPU/GPU usage.

Also add current actual frame rate to about dialog of GUI tools.

wpigui/src/main/native/cpp/wpigui.cpp

@@ -4,9 +4,13 @@
 
 #include "wpigui.h"
 
+#include <stdint.h>
+
 #include <algorithm>
+#include <chrono>
 #include <cstdio>
 #include <cstring>
+#include <thread>
 
 #include <GLFW/glfw3.h>
 #include <IconsFontAwesome6.h>
@@ -88,6 +92,8 @@ static void IniReadLine(ImGuiContext* ctx, ImGuiSettingsHandler* handler,
     impl->userScale = num;
   } else if (std::strncmp(lineStr, "style=", 6) == 0) {
     impl->style = num;
+  } else if (std::strncmp(lineStr, "fps=", 4) == 0) {
+    impl->fps = num;
   }
 }
 
@@ -98,9 +104,10 @@ static void IniWriteAll(ImGuiContext* ctx, ImGuiSettingsHandler* handler,
   }
   out_buf->appendf(
       "[MainWindow][GLOBAL]\nwidth=%d\nheight=%d\nmaximized=%d\n"
-      "xpos=%d\nypos=%d\nuserScale=%d\nstyle=%d\n\n",
+      "xpos=%d\nypos=%d\nuserScale=%d\nstyle=%d\nfps=%d\n\n",
       gContext->width, gContext->height, gContext->maximized ? 1 : 0,
-      gContext->xPos, gContext->yPos, gContext->userScale, gContext->style);
+      gContext->xPos, gContext->yPos, gContext->userScale, gContext->style,
+      gContext->fps);
 }
 
 void gui::CreateContext() {
@@ -331,6 +338,8 @@ bool gui::Initialize(const char* title, int width, int height,
 void gui::Main() {
   // Main loop
   while (!glfwWindowShouldClose(gContext->window) && !gContext->exit) {
+    double startTime = glfwGetTime();
+
     // Poll and handle events (inputs, window resize, etc.)
     glfwPollEvents();
     gContext->isPlatformRendering = true;
@@ -351,6 +360,15 @@ void gui::Main() {
         io.WantSaveIniSettings = false;  // reset flag
       }
     }
+
+    // if FPS limiting, sleep until next frame time
+    if (gContext->fps != 0) {
+      double sleepTime = (1.0 / gContext->fps) - (glfwGetTime() - startTime);
+      if (sleepTime > 1e-6) {
+        std::this_thread::sleep_for(
+            std::chrono::microseconds(static_cast<int64_t>(sleepTime * 1e6)));
+      }
+    }
   }
 
   // Save (if custom save)
@@ -477,6 +495,10 @@ void gui::SetStyle(Style style) {
   }
 }
 
+void gui::SetFPS(int fps) {
+  gContext->fps = fps;
+}
+
 void gui::SetClearColor(ImVec4 color) {
   gContext->clearColor = color;
 }
@@ -539,6 +561,27 @@ void gui::EmitViewMenu() {
       ImGui::EndMenu();
     }
 
+    if (ImGui::BeginMenu("Frame Rate")) {
+      bool selected;
+      selected = gContext->fps == 0;
+      if (ImGui::MenuItem("vsync", nullptr, &selected)) {
+        gContext->fps = 0;
+      }
+      selected = gContext->fps == 30;
+      if (ImGui::MenuItem("30 fps", nullptr, &selected)) {
+        gContext->fps = 30;
+      }
+      selected = gContext->fps == 60;
+      if (ImGui::MenuItem("60 fps", nullptr, &selected)) {
+        gContext->fps = 60;
+      }
+      selected = gContext->fps == 120;
+      if (ImGui::MenuItem("120 fps", nullptr, &selected)) {
+        gContext->fps = 120;
+      }
+      ImGui::EndMenu();
+    }
+
     if (!gContext->saveSettings) {
       ImGui::MenuItem("Reset UI on Exit?", nullptr, &gContext->resetOnExit);
     }