feat: ease automatic ink colour transitions

Author: Fryingpan-Jason

src/glass_auto_ink.h

@@ -43,4 +43,23 @@ struct Decision {
         if(now-candidateAt>=90){white=next;pending=false;}
     }
 };
+struct Fade {
+    static constexpr double duration=180;
+    COLORREF from=Dark,target=Dark;
+    double started=0;
+    bool initialized=false;
+    void Reset(COLORREF colour){from=target=colour;initialized=true;started=0;}
+    bool Running(double now) const {return from!=target && now-started<duration;}
+    COLORREF Sample(double now) const {
+        double t=std::clamp((now-started)/duration,0.,1.);
+        t=t*t*(3-2*t); // smooth departure and arrival, no long grey plateau
+        auto channel=[t](int a,int b){return int(std::lround(a+(b-a)*t));};
+        return RGB(channel(GetRValue(from),GetRValue(target)),channel(GetGValue(from),GetGValue(target)),channel(GetBValue(from),GetBValue(target)));
+    }
+    void Aim(COLORREF colour,COLORREF current,double now) {
+        if(!initialized)Reset(current);
+        if(colour==target)return;
+        from=Sample(now);target=colour;started=now;
+    }
+};
 }

src/main.cpp

@@ -592,18 +592,34 @@ void RequestRender() {
 #ifdef FLOATNOTE_GLASS_LAB
 void SyncAdaptiveInk() {
     static bool timer=false;
+    static bool fadeTimer=false;
+    static GlassAutoInk::Fade fade;
+    static double lastInkPaint=0;
     const bool motion=ExperienceAbsorbing();
     const bool active=g_window && g_settings.autoTextColor && !g_highContrast && g_nativeGlass && g_glassActive &&
         g_backdrop.mode==2 && EffectiveOpacityPercent()<100 && g_isVisible && !IsIconic(g_window) && !ExperienceCompact();
     if(active && !motion && !timer){SetTimer(g_window,82,100,nullptr);timer=true;}
     else if((!active || motion) && timer){KillTimer(g_window,82);timer=false;}
-    if(motion)return; // Freeze the chosen ink through the cached-surface animation.
+    if(motion) {
+        if(fadeTimer){KillTimer(g_window,83);fadeTimer=false;}
+        fade.Reset(kNoteText);return; // Freeze ink through the cached-surface animation.
+    }
     const int alpha=std::max(g_settings.passThrough?0:1,MulDiv(EffectiveOpacityPercent(),255,100));
     const int choice=g_backdrop.UpdateAutoInk(active,kBackground,alpha,kText==GlassAutoInk::Light);
     const COLORREF next=g_highContrast?kText:!g_settings.autoTextColor?g_settings.textColor:
         choice<0?kText:choice?GlassAutoInk::Light:GlassAutoInk::Dark;
-    if(next!=kNoteText) {
-        kNoteText=next;
+    const double now=GlassClockMs();
+    if(active && choice>=0)fade.Aim(next,kNoteText,now);
+    else fade.Reset(next); // Explicit colours and accessibility changes apply immediately.
+    const bool animating=active && fade.Running(now);
+    if(animating && !fadeTimer){SetTimer(g_window,83,16,nullptr);fadeTimer=true;}
+    else if(!animating && fadeTimer){KillTimer(g_window,83);fadeTimer=false;}
+    // Capture and render-completion events also enter here. Cap fade updates
+    // so they cannot turn a short animation into a self-posting repaint loop.
+    const COLORREF presented=animating && now-lastInkPaint<16?kNoteText:fade.Sample(now);
+    if(presented!=kNoteText) {
+        lastInkPaint=now;
+        kNoteText=presented;
         if(g_edit)InvalidateRect(g_edit,nullptr,FALSE);
         RequestRender();
     }
@@ -2434,6 +2450,7 @@ LRESULT CALLBACK WindowProcedure(HWND window, UINT message, WPARAM wParam, LPARA
     if (message == WM_TIMER && wParam == 71) { g_backdrop.Tick(); SyncAdaptiveInk(); return 0; }
     if (message == kGlassFrameReady) { g_backdrop.FrameReady(); SyncAdaptiveInk(); ApplyWindowStacking(); return 0; }
     if (message == WM_TIMER && wParam == 82) { SyncAdaptiveInk(); return 0; }
+    if (message == WM_TIMER && wParam == 83) { SyncAdaptiveInk(); return 0; }
     if (message == WM_WINDOWPOSCHANGED) {g_backdrop.RequestDraw();SyncExperienceUI();}
     if (message == WM_ACTIVATE && LOWORD(wParam)!=WA_INACTIVE)SyncExperienceUI();
     if (message == WM_TIMER && wParam==73){ApplyWindowStacking();SyncExperienceUI();return 0;}

tests/glass_auto_ink_native.cpp

@@ -13,6 +13,12 @@ struct GlassAutoInkTest {
     }
     static void Check(bool ok,const char* error){if(!ok)throw std::runtime_error(error);}
     static void Run() {
+        GlassAutoInk::Fade fade;fade.Reset(GlassAutoInk::Dark);fade.Aim(GlassAutoInk::Light,GlassAutoInk::Dark,1000);
+        Check(fade.Sample(1000)==GlassAutoInk::Dark,"fade jumped at start");
+        const COLORREF middle=fade.Sample(1090);
+        Check(GetRValue(middle)>GetRValue(GlassAutoInk::Dark) && GetRValue(middle)<GetRValue(GlassAutoInk::Light),"fade lacks intermediate colour");
+        fade.Aim(GlassAutoInk::Dark,middle,1090);Check(fade.Sample(1090)==middle,"fade reversal jumped");
+        Check(fade.Sample(1270)==GlassAutoInk::Dark && !fade.Running(1270),"fade failed to settle");
         g_instance=GetModuleHandleW(nullptr);
         g_window=CreateWindowExW(WS_EX_TOOLWINDOW,L"STATIC",L"Hidden ink test",WS_POPUP,0,0,320,160,nullptr,nullptr,g_instance,nullptr);
         g_edit=CreateWindowExW(0,L"EDIT",L"Editable text",WS_CHILD|ES_MULTILINE,0,0,200,100,g_window,nullptr,g_instance,nullptr);
@@ -22,7 +28,8 @@ struct GlassAutoInkTest {
         kBackground=RGB(255,255,255);kText=kNoteText=GlassAutoInk::Dark;
         SendMessageW(g_edit,EM_SETSEL,0,1);SendMessageW(g_edit,EM_REPLACESEL,TRUE,reinterpret_cast<LPARAM>(L"X"));
         DWORD beforeStart=0,beforeEnd=0;SendMessageW(g_edit,EM_GETSEL,reinterpret_cast<WPARAM>(&beforeStart),reinterpret_cast<LPARAM>(&beforeEnd));
-        Seed();SyncAdaptiveInk();Check(kNoteText==GlassAutoInk::Light,"Auto did not apply sampled white ink");
+        Seed();SyncAdaptiveInk();Check(kNoteText==GlassAutoInk::Dark,"Auto ink did not start smoothly");
+        Sleep(200);SyncAdaptiveInk();Check(kNoteText==GlassAutoInk::Light,"Auto did not settle on sampled white ink");
         Check(kText==GlassAutoInk::Dark,"Auto recoloured settings UI");
         DWORD afterStart=0,afterEnd=0;SendMessageW(g_edit,EM_GETSEL,reinterpret_cast<WPARAM>(&afterStart),reinterpret_cast<LPARAM>(&afterEnd));
         Check(afterStart==beforeStart&&afterEnd==beforeEnd&&SendMessageW(g_edit,EM_CANUNDO,0,0),"ink update disturbed native selection/undo");