WPF - IME Only use GCS_CURSORPOS if an adjacent character is new input (

cefsharp#3846) * Change Wpf IME handling to only use the cursor pos when an adjacent character is new input * Meant to change both character before and after * Ensure the cursor pos is > 0 when checking the character before
odo-leni · Oct 11, 2021 · bfa8ccf · bfa8ccf
1 parent 544abc6
commit bfa8ccf
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Showing 2 changed files with 22 additions and 3 deletions.
diff --git a/CefSharp.Wpf/Internals/IMEHandler.cs b/CefSharp.Wpf/Internals/IMEHandler.cs
@@ -75,11 +75,12 @@ private static void GetCompositionInfo(IntPtr hwnd, uint lParam, string text, Li
 
             underlines.Clear();
 
+            byte[] attributes = null;
             int targetStart = text.Length;
             int targetEnd = text.Length;
             if (IsParam(lParam, ImeNative.GCS_COMPATTR))
             {
-                GetCompositionSelectionRange(hIMC, ref targetStart, ref targetEnd);
+                attributes = GetCompositionSelectionRange(hIMC, ref targetStart, ref targetEnd);
             }
 
             // Retrieve the selection range information. If CS_NOMOVECARET is specified
@@ -98,6 +99,22 @@ private static void GetCompositionInfo(IntPtr hwnd, uint lParam, string text, Li
                 compositionStart = 0;
             }
 
+            if (attributes != null &&
+                // character before
+                ((compositionStart > 0 && (compositionStart - 1) < attributes.Length && attributes[compositionStart - 1] == ImeNative.ATTR_INPUT)
+                ||
+                // character after
+                (compositionStart >= 0 && compositionStart < attributes.Length && attributes[compositionStart] == ImeNative.ATTR_INPUT)))
+            {
+                // as MS does with their ime implementation we should only use the GCS_CURSORPOS if the character
+                // before or after is new input.
+                // https://referencesource.microsoft.com/#PresentationFramework/src/Framework/System/windows/Documents/ImmComposition.cs,1079
+            }
+            else
+            {
+                compositionStart = text.Length;
+            }
+
             if (IsParam(lParam, ImeNative.GCS_COMPCLAUSE))
             {
                 GetCompositionUnderlines(hIMC, targetStart, targetEnd, underlines);
@@ -158,12 +175,12 @@ private static void GetCompositionUnderlines(IntPtr hIMC, int targetStart, int t
             }
         }
 
-        private static void GetCompositionSelectionRange(IntPtr hIMC, ref int targetStart, ref int targetEnd)
+        private static byte[] GetCompositionSelectionRange(IntPtr hIMC, ref int targetStart, ref int targetEnd)
         {
             var attributeSize = ImeNative.ImmGetCompositionString(hIMC, ImeNative.GCS_COMPATTR, null, 0);
             if (attributeSize <= 0)
             {
-                return;
+                return null;
             }
 
             int start = 0;
@@ -191,6 +208,7 @@ private static void GetCompositionSelectionRange(IntPtr hIMC, ref int targetStar
 
             targetStart = start;
             targetEnd = end;
+            return attributeData;
         }
 
         private static bool IsSelectionAttribute(byte attribute)

diff --git a/CefSharp.Wpf/Internals/ImeNative.cs b/CefSharp.Wpf/Internals/ImeNative.cs
@@ -19,6 +19,7 @@ public static class ImeNative
         internal const uint CS_NOMOVECARET = 0x4000;
         internal const uint NI_COMPOSITIONSTR = 0x0015;
 
+        internal const uint ATTR_INPUT = 0x00;
         internal const uint ATTR_TARGET_CONVERTED = 0x01;
         internal const uint ATTR_TARGET_NOTCONVERTED = 0x03;