Fix InputBox drag cursor regression and IME selection-delete

[Copilot]

• Fix Issue 1: cursor follows drag
• Fix Issue 2: IME clears selection before composition
• Extract applyDragMove helper
• Fix cursor forced to end of selection after mouse release
• Fix unwanted selection after click-to-cancel-IME
  • Root cause: ImmNotifyIME(CPS_COMPLETE) in killIME() triggers WM_IME_COMPOSITION(GCS_RESULTSTR), which makes the EDIT insert the committed text and move its cursor to after the inserted text; the draw-loop EM_GETSEL sync then sees a displaced cursor, decides selMatchesOurs is false, and creates an unwanted [click_pos, commit_end] selection
  • Fix: capture getCursorPos() (= click position) before killIME(), then call movecursor(savedPos, savedPos) after — the draw-loop sync now sees EM_GETSEL == (dragBegin, dragEnd) so selMatchesOurs is true and no spurious selection is applied

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[Copilot]

Pull request overview

Fixes InputBox drag-selection cursor behavior and IME composition behavior by removing a destructive async cursor update from EM_SETSEL, and by explicitly deleting the active selection before IME composition begins. Also refactors drag-move handling into a shared helper to keep selection updates working when the mouse leaves nested Panel bounds.

Changes:

• Stop posting async WM_USER+100+1 after EM_SETSEL to prevent cursor being reset to the selection anchor during drag.
• Add InputBox::deleteSelectedText() and invoke it from WM_IME_STARTCOMPOSITION so IME composition correctly replaces the active selection.
• Refactor and expand drag-move handling via applyDragMove() across handleEvent, catchMouseOwningFlag, and releaseMouseOwningFlag, plus draw-time sync/highlight updates.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
src/sys_edit.cpp	IME start-composition now deletes selection; EM_SETSEL no longer triggers async cursor reset.
src/Widget.cpp	Drag selection refactor (applyDragMove, charPositionFromLocalX), draw-time selection sync/highlight, selection deletion helper, updated mouse owning behavior.
include/Widget.h	Declares new InputBox helper APIs (charPositionFromLocalX, applyDragMove, deleteSelectedText).

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[Copilot]

Selection highlight drawing measures content.substr(0, sel_s/sel_e) every frame while focused with a selection. For long strings, this adds extra per-frame substring creation + text measurement on top of the existing cursor/IME measurements. Consider reusing the existing measurement cache (or caching prefix widths / last selection bounds) to avoid redundant measuretext() work during repaint.

Suggested change

	float sel_s_px, sel_e_px, sel_tmp;
	measuretext(content.substr(0, sel_s).c_str(), &sel_s_px, &sel_tmp, btnLayer);
	measuretext(content.substr(0, sel_e).c_str(), &sel_e_px, &sel_tmp, btnLayer);
	// 缓存选区起止位置对应的像素宽度，避免每帧重复 substr + measuretext
	static std::wstring lastSelMeasuredContent;
	static int lastSelS = -1;
	static int lastSelE = -1;
	static bool lastSelScaleChanged = false;
	static bool lastSelPanelScaleChanged = false;
	static float cachedSelSPx = 0.0f;
	static float cachedSelEPx = 0.0f;
	bool needRemeasureSelection =
	lastSelMeasuredContent != content ||
	lastSelS != sel_s ||
	lastSelE != sel_e ||
	lastSelScaleChanged != scaleChanged ||
	lastSelPanelScaleChanged != PanelScaleChanged;
	float sel_s_px;
	float sel_e_px;
	float sel_tmp;
	if (needRemeasureSelection) {
	measuretext(content.substr(0, sel_s).c_str(), &sel_s_px, &sel_tmp, btnLayer);
	measuretext(content.substr(0, sel_e).c_str(), &sel_e_px, &sel_tmp, btnLayer);
	cachedSelSPx = sel_s_px;
	cachedSelEPx = sel_e_px;
	lastSelMeasuredContent = content;
	lastSelS = sel_s;
	lastSelE = sel_e;
	lastSelScaleChanged = scaleChanged;
	lastSelPanelScaleChanged = PanelScaleChanged;
	} else {
	sel_s_px = cachedSelSPx;
	sel_e_px = cachedSelEPx;
	}

[Copilot]

charPositionFromLocalX() does repeated content.substr(0, mid) allocations + measuretext() calls in a binary search. This used to run only on mouse-down, but it’s now called on every mouse-move during selection (applyDragMove), which can become noticeably expensive for longer text / high-frequency mouse events. Consider caching prefix pixel widths when content changes (or otherwise avoid repeated substring allocations/measures) so drag-selection stays smooth.

[FeJS8888]

@copilot 现在鼠标松开后，光标会被强制定位到选区末尾，修复这个问题

[Copilot]

@copilot 现在鼠标松开后，光标会被强制定位到选区末尾，修复这个问题

Fixed in 212303c.

Root cause: EM_GETSEL always returns a normalized (start ≤ end) pair. After a right-to-left drag (dragBegin=5, dragEnd=2), the draw-loop sync block was reading newEnd=5 and calling moveCursor(5), snapping the cursor to the far end instead of where the mouse was released.

Fix: skip the cursor+selection sync when EM_GETSEL returns exactly the normalized form of our (dragBegin, dragEnd) — this means no keyboard action has changed the selection, so cursor_pos is already correct at dragEnd (the actual release point).

[FeJS8888]

@copilot 我刚刚修复了有IME的时候点击输入框取消IME，并且提交未完成字符串，但是现在点击输入框其他位置取消IME后，会选中从提交字符串开头到点击位置的字符串，修复这个问题

[Copilot]

@copilot 我刚刚修复了有IME的时候点击输入框取消IME，并且提交未完成字符串，但是现在点击输入框其他位置取消IME后，会选中从提交字符串开头到点击��...

Fixed in e207e21.

Root cause: killIME() calls ImmNotifyIME(CPS_COMPLETE), which causes the EDIT control to process WM_IME_COMPOSITION(GCS_RESULTSTR) — inserting the committed text and moving the EDIT cursor to after the inserted text. The draw-loop EM_GETSEL sync then sees this displaced cursor, finds selMatchesOurs is false, and overwrites dragBegin/dragEnd with a range spanning from the click position to the commit-end position, creating the unwanted selection highlight.

Fix: in the WM_USER+100+2 handler, capture the EDIT cursor position (= the click position — WM_SETTEXT doesn't move the cursor so it's still correct) before calling killIME(), then restore it with movecursor(savedPos, savedPos) afterwards. The draw-loop sync then reads EM_GETSEL == (dragBegin, dragEnd), selMatchesOurs is true, and no spurious selection is applied.