From 5dc25cb95ae69b7102aa2ead075ab9277fa8db72 Mon Sep 17 00:00:00 2001
From: Neil <nyamatongwe@gmail.com>
Date: Tue, 5 Mar 2019 08:35:51 +1100
Subject: Backport: Implement QueueIdleWork on Win32.

Backport fo changeset 7316:a726290d864a.
---
 doc/ScintillaHistory.html |  3 +++
 win32/ScintillaWin.cxx    | 33 ++++++++++++++++++++++++++++++++-
 2 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/doc/ScintillaHistory.html b/doc/ScintillaHistory.html
index 4b00440b4..3f0735e58 100644
--- a/doc/ScintillaHistory.html
+++ b/doc/ScintillaHistory.html
@@ -557,6 +557,9 @@
 	On Win32, removed special handling of non-0 wParam to WM_PAINT.
 	</li>
  	<li>
+	Implement high-priority idle on Win32 to make redraw smoother and more efficient.
+	</li>
+ 	<li>
 	Avoid potential long hangs with idle styling for huge documents on Cocoa and GTK.
 	</li>
     <ul>
diff --git a/win32/ScintillaWin.cxx b/win32/ScintillaWin.cxx
index e88cebe6c..dd6688e5b 100644
--- a/win32/ScintillaWin.cxx
+++ b/win32/ScintillaWin.cxx
@@ -117,7 +117,15 @@
 #define MK_ALT 32
 #endif
 
-#define SC_WIN_IDLE 5001
+// Two idle messages SC_WIN_IDLE and SC_WORK_IDLE.
+
+// SC_WIN_IDLE is low priority so should occur after the next WM_PAINT
+// It is for lengthy actions like wrapping and background styling 
+constexpr UINT SC_WIN_IDLE = 5001;
+// SC_WORK_IDLE is high priority and should occur before the next WM_PAINT
+// It is for shorter actions like restyling the text just inserted
+// and delivering SCN_UPDATEUI
+constexpr UINT SC_WORK_IDLE = 5002;
 
 #define SC_INDICATOR_INPUT INDIC_IME
 #define SC_INDICATOR_TARGET INDIC_IME+1
@@ -337,6 +345,8 @@ class ScintillaWin :
 	UINT CodePageOfDocument() const;
 	bool ValidCodePage(int codePage) const override;
 	sptr_t DefWndProc(unsigned int iMessage, uptr_t wParam, sptr_t lParam) override;
+	void IdleWork() override;
+	void QueueIdleWork(WorkNeeded::workItems items, Sci::Position upTo) override;
 	bool SetIdle(bool on) override;
 	UINT_PTR timers[tickDwell+1] {};
 	bool FineTickerRunning(TickReason reason) override;
@@ -426,6 +436,7 @@ private:
 	HBITMAP sysCaretBitmap;
 	int sysCaretWidth;
 	int sysCaretHeight;
+	bool styleIdleInQueue;
 };
 
 HINSTANCE ScintillaWin::hInstance {};
@@ -472,6 +483,8 @@ ScintillaWin::ScintillaWin(HWND hwnd) {
 	sysCaretWidth = 0;
 	sysCaretHeight = 0;
 
+	styleIdleInQueue = false;
+
 #if defined(USE_D2D)
 	pRenderTarget = nullptr;
 	renderTargetValid = true;
@@ -1378,6 +1391,10 @@ sptr_t ScintillaWin::WndProc(unsigned int iMessage, uptr_t wParam, sptr_t lParam
 			}
 			break;
 
+		case SC_WORK_IDLE:
+			IdleWork();
+			break;
+
 		case WM_GETMINMAXINFO:
 			return ::DefWindowProc(MainHWND(), iMessage, wParam, lParam);
 
@@ -1810,6 +1827,20 @@ bool ScintillaWin::SetIdle(bool on) {
 	return idler.state;
 }
 
+void ScintillaWin::IdleWork() {
+	styleIdleInQueue = false;
+	Editor::IdleWork();
+}
+
+void ScintillaWin::QueueIdleWork(WorkNeeded::workItems items, Sci::Position upTo) {
+	Editor::QueueIdleWork(items, upTo);
+	if (!styleIdleInQueue) {
+		if (PostMessage(MainHWND(), SC_WORK_IDLE, 0, 0)) {
+			styleIdleInQueue = true;
+		}
+	}
+}
+
 void ScintillaWin::SetMouseCapture(bool on) {
 	if (mouseDownCaptures) {
 		if (on) {
-- 
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