Take the WinForms shell from PlatformHeads.WindowsForms

.github/workflows/build-native.yml

@@ -35,7 +35,7 @@ concurrency:
 
 jobs:
   native:
-    uses: SimonCropp/PlatformHeads/.github/workflows/build-native.yml@0.2.0
+    uses: SimonCropp/PlatformHeads/.github/workflows/build-native.yml@0.3.0
     permissions:
       contents: write
       pull-requests: write

claude.md

@@ -253,7 +253,7 @@ the comment there about not caching "nothing staged" asks for.
   own loop for every part of the scroll bar, not the thumb alone, and `Present` stops that timer.
   An Alt chord is no command. A held key gives one accept or discard (the repeat flag, read in
   `ProcessCmdKey`, for what `ViewerSession.ChangesQueue` names), while navigation keeps its
-  repeats. A minimised window waits between frames as a hidden one does. The footer wraps its buttons, and
+  repeats. The form is a `HeadForm` from PlatformHeads.WindowsForms, which opens it where it was left, turns a close into a request, brings a maximised window back maximised, keeps frames coming inside user32's own loops (`ViewerForm.Frame` hands it `ModalFrame`), and idles in `WaitForFrame`: the loop waits there on the message queue and its `LoopWake` together, until input, a change of state or a window command, which `MessageHandler` and `OwnerLink.Commanded` set it for, and no longer than a frame while a spinner is up. It woke sixty times a second with nothing to do. A fix to any of that goes to PlatformHeads. The footer wraps its buttons, and
   gives a status with no room beside them lines of its own under them (`LayOutFooter`), as the
   other two heads do; the buttons are the footer's own children, and a taller footer comes off the
   canvas, which reports the rows it has left. A decoded picture is kept premultiplied, as the
@@ -615,10 +615,10 @@ the comment there about not caching "nothing staged" asks for.
 **Native shim (`native/`), used by the Mac and Linux heads only:**
 - The build and packaging of the heads is PlatformHeads' (`D:\Code\PlatformHeads`,
   github.com/SimonCropp/PlatformHeads), which BuildMonitor shares: it was worked out here and
-  copied there, and fixes made here did not reach the copy. Four pins name one tag of it and move
+  copied there, and fixes made here did not reach the copy. Five pins name one tag of it and move
   together: the `uses:` of `.github/workflows/build-native.yml`, the `GIT_TAG` in
-  `native/CMakeLists.txt`, and `PlatformHeads` and `PlatformHeads.Core` in
-  `Directory.Packages.props`. The workflow is its
+  `native/CMakeLists.txt`, and `PlatformHeads`, `PlatformHeads.Core` and
+  `PlatformHeads.WindowsForms` in `Directory.Packages.props`. The workflow is its
   reusable `build-native`. Its CMake module pins raylib and Dear ImGui, carries the raylib 6.0
   option workarounds and links the library, and `native/CMakeLists.txt` names only the picture
   formats, the source file and the two libraries the viewer links beyond raylib. Its package's

native/CMakeLists.txt

@@ -15,7 +15,7 @@ include(FetchContent)
 FetchContent_Declare(
   platformheads
   GIT_REPOSITORY https://github.com/SimonCropp/PlatformHeads.git
-  GIT_TAG 0.2.0
+  GIT_TAG 0.3.0
   GIT_SHALLOW ON)
 FetchContent_MakeAvailable(platformheads)
 include(${platformheads_SOURCE_DIR}/cmake/PlatformHeads.cmake)

src/DiffEngineViewer.Windows.Tests/FormsHeadTests.cs

@@ -715,10 +715,10 @@ screen with
     [Test]
     public async Task TheFirstWindowIsSizedForTheDisplay()
     {
-        await Assert.That(ViewerForm.InitialClientSize(new(1100, 700), 96, new(1920, 1040))).IsEqualTo(new(1100, 700));
-        await Assert.That(ViewerForm.InitialClientSize(new(1100, 700), 192, new(3840, 2100))).IsEqualTo(new(2200, 1400));
+        await Assert.That(WindowFit.InitialClientSize(new(1100, 700), 96, new(1920, 1040))).IsEqualTo(new(1100, 700));
+        await Assert.That(WindowFit.InitialClientSize(new(1100, 700), 192, new(3840, 2100))).IsEqualTo(new(2200, 1400));
         // 1050 tall at 150% does not fit a 1080p working area, and is kept inside it
-        await Assert.That(ViewerForm.InitialClientSize(new(1100, 700), 144, new(1920, 1040))).IsEqualTo(new(1650, 936));
+        await Assert.That(WindowFit.InitialClientSize(new(1100, 700), 144, new(1920, 1040))).IsEqualTo(new(1650, 936));
     }
 
     /// <summary>
@@ -743,7 +743,7 @@ public async Task WhatTheFirstWindowHoldsAtEachScale()
             // Straight from user32: SystemInformation answers 17 at every DPI in an unaware host.
             var bar = GetSystemMetricsForDpi(verticalScrollBarWidth, (uint) dpi);
             var footer = 40 * dpi / 96;
-            var window = ViewerForm.InitialClientSize(new(1100, 700), dpi, new(3840, 2100));
+            var window = WindowFit.InitialClientSize(new(1100, 700), dpi, new(3840, 2100));
             host.Resize(window.Width - bar, window.Height - footer);
             typeof(ViewerCanvas).GetField("cell", BindingFlags.Instance | BindingFlags.NonPublic)!.SetValue(host.Canvas, cell);
             host.Canvas.Draw(screen);
@@ -1279,8 +1279,22 @@ static string Lines(int count, int changedAt = -1)
         return builder.ToString();
     }
 
-    static T Field<T>(object target, string name) =>
-        (T) target.GetType().GetField(name, BindingFlags.Instance | BindingFlags.NonPublic)!.GetValue(target)!;
+    /// <summary>
+    /// A private field of <paramref name="target"/> or of a class it derives from: the modal frame
+    /// timer is HeadForm's, and reflection does not look in a base class for a private field.
+    /// </summary>
+    static T Field<T>(object target, string name)
+    {
+        for (var type = target.GetType(); type is not null; type = type.BaseType)
+        {
+            if (type.GetField(name, BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.DeclaredOnly) is { } field)
+            {
+                return (T) field.GetValue(target)!;
+            }
+        }
+
+        throw new MissingFieldException(target.GetType().Name, name);
+    }
 
     static (int Cell, float Advance) Measure(Font font, int dpi)
     {

src/DiffEngineViewer.Windows.Tests/WindowPlacementTests.cs

@@ -13,7 +13,7 @@ public class WindowPlacementTests
     [Test]
     public async Task AWindowOnADisplayOpensWhereItWas()
     {
-        var restored = ViewerForm.Restorable(new(300, 200, 1100, 700, false), [display]);
+        var restored = WindowFit.Restorable(new(300, 200, 1100, 700, false), [display]);
 
         await Assert.That(restored).IsEqualTo(new Rectangle(300, 200, 1100, 700));
     }
@@ -25,15 +25,15 @@ public async Task AWindowOnADisplayOpensWhereItWas()
     [Test]
     public async Task ASnappedWindowIsLeftExactlyWhereItWas()
     {
-        var restored = ViewerForm.Restorable(new(-7, 0, 974, 1047, false), [display]);
+        var restored = WindowFit.Restorable(new(-7, 0, 974, 1047, false), [display]);
 
         await Assert.That(restored).IsEqualTo(new Rectangle(-7, 0, 974, 1047));
     }
 
     [Test]
     public async Task AWindowOnTheSecondDisplayOpensThere()
     {
-        var restored = ViewerForm.Restorable(new(2200, 100, 1500, 900, false), [display, second]);
+        var restored = WindowFit.Restorable(new(2200, 100, 1500, 900, false), [display, second]);
 
         await Assert.That(restored).IsEqualTo(new Rectangle(2200, 100, 1500, 900));
     }
@@ -45,15 +45,15 @@ public async Task AWindowOnTheSecondDisplayOpensThere()
     [Test]
     public async Task AWindowOnADisplayThatHasGoneIsNotUsed()
     {
-        var restored = ViewerForm.Restorable(new(2200, 100, 1500, 900, false), [display]);
+        var restored = WindowFit.Restorable(new(2200, 100, 1500, 900, false), [display]);
 
         await Assert.That(restored).IsNull();
     }
 
     [Test]
     public async Task AWindowMostlyOffADisplayIsMovedOntoIt()
     {
-        var restored = ViewerForm.Restorable(new(1700, 800, 1100, 700, false), [display]);
+        var restored = WindowFit.Restorable(new(1700, 800, 1100, 700, false), [display]);
 
         await Assert.That(restored).IsEqualTo(new Rectangle(820, 340, 1100, 700));
     }
@@ -65,7 +65,7 @@ public async Task AWindowMostlyOffADisplayIsMovedOntoIt()
     [Test]
     public async Task AWindowWithItsTitleBarOffTheTopIsMovedDown()
     {
-        var restored = ViewerForm.Restorable(new(300, -200, 1100, 900, false), [display]);
+        var restored = WindowFit.Restorable(new(300, -200, 1100, 900, false), [display]);
 
         await Assert.That(restored).IsEqualTo(new Rectangle(300, 0, 1100, 900));
     }
@@ -76,15 +76,15 @@ public async Task AWindowWithItsTitleBarOffTheTopIsMovedDown()
     [Test]
     public async Task AWindowLargerThanTheDisplayIsCutToIt()
     {
-        var restored = ViewerForm.Restorable(new(100, 100, 3000, 2000, false), [display]);
+        var restored = WindowFit.Restorable(new(100, 100, 3000, 2000, false), [display]);
 
         await Assert.That(restored).IsEqualTo(new Rectangle(0, 0, 1920, 1040));
     }
 
     [Test]
     public async Task AWindowTooSmallToHaveBeenLeftIsNotUsed()
     {
-        var restored = ViewerForm.Restorable(new(300, 200, 40, 20, false), [display]);
+        var restored = WindowFit.Restorable(new(300, 200, 40, 20, false), [display]);
 
         await Assert.That(restored).IsNull();
     }
@@ -106,15 +106,15 @@ public async Task AFirstWindowIsCentredForTheSizeItOpensAt()
 
         var area = System.Windows.Forms.Screen.FromControl(form).WorkingArea;
         await Assert.That(form.Width).IsLessThan(area.Width);
-        await Assert.That(form.Location).IsEqualTo(ViewerForm.Centred(area, form.Size));
+        await Assert.That(form.Location).IsEqualTo(WindowFit.Centred(area, form.Size));
         await Assert.That(form.Left).IsGreaterThan(area.Left);
     }
 
     [Test]
     public async Task CentredIsTheMiddleOfTheDisplayItIsOn()
     {
-        await Assert.That(ViewerForm.Centred(display, new(1100, 700))).IsEqualTo(new(410, 170));
-        await Assert.That(ViewerForm.Centred(second, new(1500, 900))).IsEqualTo(new(2450, 250));
+        await Assert.That(WindowFit.Centred(display, new(1100, 700))).IsEqualTo(new(410, 170));
+        await Assert.That(WindowFit.Centred(second, new(1500, 900))).IsEqualTo(new(2450, 250));
     }
 
     /// <summary>
@@ -123,7 +123,7 @@ public async Task CentredIsTheMiddleOfTheDisplayItIsOn()
     /// </summary>
     [Test]
     public async Task AWindowLargerThanTheDisplayIsCentredFromItsTopLeft() =>
-        await Assert.That(ViewerForm.Centred(second, new(3000, 1600))).IsEqualTo(new(1920, 0));
+        await Assert.That(WindowFit.Centred(second, new(3000, 1600))).IsEqualTo(new(1920, 0));
 
     [Test]
     public async Task AFormOpensAtTheBoundsItIsGiven()

src/DiffEngineViewer.Windows/DiffEngineViewer.Windows.csproj

@@ -72,6 +72,7 @@
     <!-- And an ImageFormat, so the GDI+ one needs a name for the same reason. -->
     <Using Include="System.Drawing.Imaging.ImageFormat" Alias="DrawingImageFormat" />
     <ProjectReference Include="..\DiffEngineViewer\DiffEngineViewer.csproj" />
+    <PackageReference Include="PlatformHeads.WindowsForms" />
     <PackageReference Include="ProjectDefaults" PrivateAssets="all" />
     <None Include="..\DiffEngineViewer\Assets\JetBrainsMono-OFL.txt" Pack="true" PackagePath="\" />
     <None Remove="viewer.ico" />

src/DiffEngineViewer.Windows/FormsViewerWindow.cs

@@ -15,12 +15,6 @@ sealed class FormsViewerWindow :
     IViewerWindow,
     ILoopHooks
 {
-    /// <summary>
-    /// Roughly sixty frames a second, which is what the shim's SetTargetFPS gives the other heads.
-    /// Without it this loop would spin a core, since DoEvents returns immediately when idle.
-    /// </summary>
-    const int frameMilliseconds = 16;
-
     readonly ViewerForm form;
     bool disposed;
 
@@ -70,48 +64,25 @@ public bool Present(Screen screen)
             return false;
         }
 
-        Wait();
         return true;
     }
 
     /// <summary>
-    /// Until the next frame is due or input arrives, whichever is first. Thread.Sleep(16) woke on
-    /// the default 15.6ms timer tick after the one it asked for, so about 31ms: half the frame
-    /// rate, with every key and click waiting out the rest of it. 15 lands on the next tick, and
-    /// input ends the wait at once. Hidden, which a tray keeps it for days, there is nothing to
-    /// draw, so it wakes a few times a second rather than sixty.
+    /// HeadForm's: idles on the message queue and the loop's wake together, a frame at most while
+    /// a spinner is up, and not at all while input is already waiting. It woke sixty times a
+    /// second with the window open and nothing happening, and ten hidden or minimised.
     /// </summary>
-    void Wait()
+    public bool Wait(TimeSpan timeout, WaitHandle wake)
     {
-        // Input already waiting is the next frame's, now: a key and a click that land together are
-        // two frames, and sleeping between them would put the second a frame behind for nothing.
-        if (form.Pending)
+        if (disposed || form.IsDisposed)
         {
-            return;
+            return false;
         }
 
-        var timeout = FrameWait(form.Visible, form.WindowState);
-        MsgWaitForMultipleObjectsEx(0, IntPtr.Zero, (uint) timeout, allInput, inputAvailable);
+        form.WaitForFrame(timeout, wake);
+        return true;
     }
 
-    /// <summary>
-    /// How long to wait for the next frame. A minimised window waits as a hidden one does: it is
-    /// still Visible to WinForms, so it went on at sixty frames a second with nothing of it on
-    /// screen, for as long as it sat in the taskbar. Not a third state, because what a hidden
-    /// window has to hear is what a minimised one has to: the wait ends on any message, which is
-    /// the click that restores it, and the loop reads what the listener queued each time it wakes,
-    /// so a snapshot that arrives raises the window within a tenth of a second either way.
-    /// </summary>
-    internal static int FrameWait(bool visible, FormWindowState state) =>
-        visible && state != FormWindowState.Minimized ? frameMilliseconds - 1 : hiddenMilliseconds;
-
-    const int hiddenMilliseconds = 100;
-    const uint allInput = 0x04FF;
-    const uint inputAvailable = 0x0004;
-
-    [DllImport("user32.dll")]
-    static extern uint MsgWaitForMultipleObjectsEx(uint count, IntPtr handles, uint milliseconds, uint wakeMask, uint flags);
-
     public ViewerInput Poll() =>
         form.IsDisposed ? default : form.Drain();
 
@@ -158,16 +129,13 @@ public void Focus()
     /// </summary>
     public bool SetClipboard(string text)
     {
-        try
+        if (FormsClipboard.Set(text, out var failure))
         {
-            Clipboard.SetText(text);
             return true;
         }
-        catch (ExternalException exception)
-        {
-            Console.Error.WriteLine($"Could not write to the clipboard: {exception.Message}");
-            return false;
-        }
+
+        Console.Error.WriteLine($"Could not write to the clipboard: {failure?.Message}");
+        return false;
     }
 
     public bool Capture(Screen screen, int width, int height, string pngPath)