Fixes button disabled when going backward

Author: ypujante

CMakeLists.txt

@@ -5,7 +5,7 @@ cmake_minimum_required(VERSION 3.28)
 
 set(wgpu-shader-toy_RELEASE_YEAR  "2025")
 set(wgpu-shader-toy_RELEASE_MONTH "02"  )
-set(wgpu-shader-toy_RELEASE_DAY   "26"  )
+set(wgpu-shader-toy_RELEASE_DAY   "27"  )
 
 set(wgpu-shader-toy_VERSION "${wgpu-shader-toy_RELEASE_YEAR}.${wgpu-shader-toy_RELEASE_MONTH}.${wgpu-shader-toy_RELEASE_DAY}")
 

src/cpp/FragmentShader.h

@@ -102,6 +102,7 @@ struct ShaderToyInputs {
   void resetTime();
   void startManualClock() { fClock.setManual(true); }
   void endManualClock() { fClock.setManual(false); }
+  constexpr bool isManualClock() const { return fClock.isManual(); }
 
   constexpr bool isEnabled() const { return fEnabled; }
   constexpr void toggleEnabled() { fEnabled = !fEnabled; }

src/cpp/MainWindow.cpp

@@ -452,7 +452,7 @@ void MainWindow::renderTimeControls()
   auto const frameCount = isKeyAlt ? 1 : 12;
 
   // Previous frame
-  ImGui::BeginDisabled(fCurrentFragmentShader->getInputs().frame == 0);
+  ImGui::BeginDisabled(fCurrentFragmentShader->getInputs().frame == 0 && !fCurrentFragmentShader->isManualClock());
   {
     static bool kClockState{};
     ImGui::PushItemFlag(ImGuiItemFlags_ButtonRepeat, true);

src/cpp/utils/Clock.h

@@ -49,6 +49,7 @@ class Clock
   void resume() { fPaused = false; }
 
   void setManual(bool iManual) { fManual = iManual; }
+  constexpr bool isManual() const { return fManual; }
 
   void reset()
   {