Add Window frame rate preferences

Engine/gapi/abstractgraphicsapi.h

@@ -522,6 +522,7 @@ namespace Tempest {
       struct Swapchain:NoCopy {
         virtual ~Swapchain()=default;
         virtual void          reset()=0;
+        virtual void          setPreferredFrameRateRange(uint32_t, uint32_t, uint32_t) {}
         virtual uint32_t      currentBackBufferIndex()=0;
         virtual NonUniqResId  syncId() const;
         virtual uint32_t      imageCount() const=0;

Engine/gapi/metal/mtswapchain.h

@@ -22,6 +22,9 @@ class MtSwapchain : public AbstractGraphicsApi::Swapchain {
     ~MtSwapchain();
 
     void          reset() override;
+#ifdef __IOS__
+    void          setPreferredFrameRateRange(uint32_t minimum, uint32_t maximum, uint32_t preferred) override;
+#endif
     uint32_t      currentBackBufferIndex() override;
     uint32_t      imageCount() const override;
     uint32_t      w() const override;

Engine/gapi/metal/mtswapchain.mm

@@ -156,6 +156,12 @@ static CGRect windowRect(UIWindow* wnd) {
   return currentImg;
   }
 
+#ifdef __IOS__
+void MtSwapchain::setPreferredFrameRateRange(uint32_t minimum, uint32_t maximum, uint32_t preferred) {
+  SystemApi::setPreferredFrameRateRange(reinterpret_cast<SystemApi::Window*>(pimpl->wnd),minimum,maximum,preferred);
+  }
+#endif
+
 void MtSwapchain::present() {
   auto pool = NsPtr<NS::AutoreleasePool>::init();
 

Engine/graphics/swapchain.cpp

@@ -44,6 +44,14 @@ void Swapchain::reset() {
   implReset();
   }
 
+void Swapchain::setPreferredFrameRate(uint32_t fps) {
+  setPreferredFrameRateRange(fps,fps,fps);
+  }
+
+void Swapchain::setPreferredFrameRateRange(uint32_t minimum, uint32_t maximum, uint32_t preferred) {
+  impl.handler->setPreferredFrameRateRange(minimum,maximum,preferred);
+  }
+
 uint32_t Swapchain::imageCount() const {
   return impl.handler->imageCount();
   }

Engine/graphics/swapchain.h

@@ -21,6 +21,15 @@ class Swapchain final {
 
     void                 reset();
 
+    // Requests a display callback rate, not a guaranteed rendering rate.
+    // Zero restores the system default. Ignored on unsupported platforms.
+    void                 setPreferredFrameRate(uint32_t fps);
+
+    // Rates are limited to the screen's maximum; minimum and preferred are
+    // clamped to the resulting range. Zero minimum means 1, zero preferred
+    // leaves the choice to the system, and zero maximum restores the default.
+    void                 setPreferredFrameRateRange(uint32_t minimum, uint32_t maximum, uint32_t preferred = 0);
+
     uint32_t             currentImage() const;
     uint32_t             imageCount() const;
     Attachment&          operator[](size_t id);

Engine/system/api/iosapi.h

@@ -19,6 +19,7 @@ class iOSApi final: SystemApi {
     Rect     implWindowClientRect(SystemApi::Window *w) override;
     bool     implSetAsFullscreen(SystemApi::Window *w, bool fullScreen) override;
     bool     implIsFullscreen(SystemApi::Window *w) override;
+    void     implSetPreferredFrameRateRange(SystemApi::Window *w, uint32_t minimum, uint32_t maximum, uint32_t preferred) override;
 
     void     implSetCursorPosition(SystemApi::Window *w, int x, int y) override;
     void     implShowCursor(SystemApi::Window *w, CursorShape cursor) override;

Engine/system/api/iosapi.mm

@@ -6,6 +6,7 @@
 #ifdef __IOS__
 
 #import  <UIKit/UIKit.h>
+#include <algorithm>
 #include <string>
 #include <thread>
 #include <TargetConditionals.h>
@@ -617,4 +618,18 @@ static void appleMain(void*) {
 
   }
 
+void iOSApi::implSetPreferredFrameRateRange(Window* w, uint32_t minimum, uint32_t maximum, uint32_t preferred) {
+  auto wx = reinterpret_cast<TempestWindow*>(w);
+  if(maximum==0) {
+    wx->displayLink.preferredFrameRateRange = CAFrameRateRangeDefault;
+    return;
+    }
+
+  maximum = std::min(maximum,uint32_t(wx.screen.maximumFramesPerSecond));
+  minimum = std::clamp(minimum,1u,maximum);
+  if(preferred!=0)
+    preferred = std::clamp(preferred,minimum,maximum);
+  wx->displayLink.preferredFrameRateRange = CAFrameRateRangeMake(minimum,maximum,preferred);
+  }
+
 #endif

Engine/system/systemapi.cpp

@@ -24,6 +24,13 @@ SystemApi::Data SystemApi::m;
 SystemApi::SystemApi() {
   }
 
+void SystemApi::implSetPreferredFrameRateRange(Window*, uint32_t, uint32_t, uint32_t) {
+  }
+
+void SystemApi::setPreferredFrameRateRange(Window *w, uint32_t minimum, uint32_t maximum, uint32_t preferred) {
+  return inst().implSetPreferredFrameRateRange(w,minimum,maximum,preferred);
+  }
+
 float SystemApi::implUiScale(Window* w) {
   // default to 1.0, on platforms without hidpi implementation
   return 1;

Engine/system/systemapi.h

@@ -45,6 +45,8 @@ class SystemApi {
     static void     destroyWindow(Window* w);
     static void     exit();
 
+    static void     setPreferredFrameRateRange(SystemApi::Window *w, uint32_t minimum, uint32_t maximum, uint32_t preferred);
+
     static Rect     windowClientRect(SystemApi::Window *w);
 
     static bool     setAsFullscreen(SystemApi::Window *w, bool fullScreen);
@@ -80,6 +82,7 @@ class SystemApi {
     virtual void     implShowCursor(SystemApi::Window *w, CursorShape show) = 0;
 
     virtual float    implUiScale(SystemApi::Window* w);
+    virtual void     implSetPreferredFrameRateRange(SystemApi::Window *w, uint32_t minimum, uint32_t maximum, uint32_t preferred);
 
     virtual bool     implIsRunning() = 0;
     virtual int      implExec(AppCallBack& cb) = 0;