Feature [feature-requests:#1310] Implement IME context with IMR_DOCUMENTFEED.

2 files changed, 52 insertions, 0 deletions

diff --git a/doc/ScintillaHistory.html b/doc/ScintillaHistory.html
index 57bdd6902..f0cb2ba43 100644
--- a/doc/ScintillaHistory.html
+++ b/doc/ScintillaHistory.html
@@ -587,6 +587,10 @@
 	Released 8 March 2023.
 	</li>
 	<li>
+	On Win32, implement IME context sensitivity with IMR_DOCUMENTFEED.
+	<a href="https://sourceforge.net/p/scintilla/feature-requests/1310/">Feature #1310</a>.
+	</li>
+	<li>
 	On Win32 remove dependence on MSIMG32.DLL  by replacing AlphaBlend
 	by GdiAlphaBlend.
 	<a href="https://sourceforge.net/p/scintilla/bugs/1923/">Bug #1923</a>.
diff --git a/win32/ScintillaWin.cxx b/win32/ScintillaWin.cxx
index 9a26cf5b7..970054f03 100644
--- a/win32/ScintillaWin.cxx
+++ b/win32/ScintillaWin.cxx
@@ -416,6 +416,7 @@ class ScintillaWin :
 	void ImeStartComposition();
 	void ImeEndComposition();
 	LRESULT ImeOnReconvert(LPARAM lParam);
+	LRESULT ImeOnDocumentFeed(LPARAM lParam) const;
 	sptr_t HandleCompositionWindowed(uptr_t wParam, sptr_t lParam);
 	sptr_t HandleCompositionInline(uptr_t wParam, sptr_t lParam);
 	static bool KoreanIME() noexcept;
@@ -1773,6 +1774,9 @@ sptr_t ScintillaWin::IMEMessage(unsigned int iMessage, uptr_t wParam, sptr_t lPa
 			if (wParam == IMR_RECONVERTSTRING) {
 				return ImeOnReconvert(lParam);
 			}
+			if (wParam == IMR_DOCUMENTFEED) {
+				return ImeOnDocumentFeed(lParam);
+			}
 			return ::DefWindowProc(MainHWND(), iMessage, wParam, lParam);
 		}
 
@@ -3127,6 +3131,50 @@ LRESULT ScintillaWin::ImeOnReconvert(LPARAM lParam) {
 	return rcSize;
 }
 
+LRESULT ScintillaWin::ImeOnDocumentFeed(LPARAM lParam) const {
+	// This is called while typing preedit string in.
+	// So there is no selection.
+	// Limit feed within one line without EOL.
+	// Look around:   lineStart |<--  |compStart| - caret - compEnd|  -->| lineEnd.
+
+	const Sci::Position curPos = CurrentPosition();
+	const Sci::Line curLine = pdoc->SciLineFromPosition(curPos);
+	const Sci::Position lineStart = pdoc->LineStart(curLine);
+	const Sci::Position lineEnd = pdoc->LineEnd(curLine);
+
+	const std::wstring rcFeed = StringDecode(RangeText(lineStart, lineEnd), CodePageOfDocument());
+	const int rcFeedLen = static_cast<int>(rcFeed.length()) * sizeof(wchar_t);
+	const int rcSize = sizeof(RECONVERTSTRING) + rcFeedLen + sizeof(wchar_t);
+
+	RECONVERTSTRING *rc = static_cast<RECONVERTSTRING *>(PtrFromSPtr(lParam));
+	if (!rc)
+		return rcSize;
+
+	wchar_t *rcFeedStart = reinterpret_cast<wchar_t*>(rc + 1);
+	memcpy(rcFeedStart, &rcFeed[0], rcFeedLen);
+
+	IMContext imc(MainHWND());
+	if (!imc.hIMC)
+		return 0;
+
+	const size_t compStrLen = imc.GetCompositionString(GCS_COMPSTR).size();
+	const int imeCaretPos = imc.GetImeCaretPos();
+	const Sci::Position compStart = pdoc->GetRelativePositionUTF16(curPos, -imeCaretPos);
+	const Sci::Position compStrOffset = pdoc->CountUTF16(lineStart, compStart);
+
+	// Fill in reconvert structure.
+	// Let IME to decide what the target is.
+	rc->dwVersion = 0; //constant
+	rc->dwStrLen = static_cast<DWORD>(rcFeed.length());
+	rc->dwStrOffset = sizeof(RECONVERTSTRING); //constant
+	rc->dwCompStrLen = static_cast<DWORD>(compStrLen);
+	rc->dwCompStrOffset = static_cast<DWORD>(compStrOffset) * sizeof(wchar_t);
+	rc->dwTargetStrLen = rc->dwCompStrLen;
+	rc->dwTargetStrOffset = rc->dwCompStrOffset;
+
+	return rcSize; // MS API says reconv structure to be returned.
+}
+
 void ScintillaWin::GetIntelliMouseParameters() noexcept {
 	// This retrieves the number of lines per scroll as configured in the Mouse Properties sheet in Control Panel
 	::SystemParametersInfo(SPI_GETWHEELSCROLLLINES, 0, &linesPerScroll, 0);