Comparer: pilot pink-dot grid overlay for pixel-level diffs

The image area is conceptually divided into a fixed-size grid in display
pixels. Each cell that contains at least one differing pixel between
the two source panes gets a small pink dot overlay. Because the cell
size is fixed in display pixels, zooming in implicitly subdivides the
source region per cell — at maximum zoom the dot resolves to a single
differing source pixel.

Per-row red diff lines in PosInfoView are removed, and the left
timeline is hidden when neither pane is a video; selecting frames is
still available for video sources.

Author: chammoru

Comparer/ComparerView.cpp

@@ -242,11 +242,97 @@ void CComparerView::OnDraw(CDC *pDC)
 		}
 	}
 
+	DrawDiffOverlay(&memDC, pDoc, pane);
+
 	pDC->BitBlt(0, mRcControls.bottom, mWCanvas, mHCanvas, &memDC, 0, 0, SRCCOPY);
 
 	mProcessing = false;
 }
 
+// Pilot: draw a pink dot in every grid cell that contains at least one pixel
+// that differs from the reference pane. Cell size is fixed in display pixels,
+// so zooming in implicitly subdivides the source region each cell covers —
+// at maximum zoom the dot resolves to an individual differing pixel.
+void CComparerView::DrawDiffOverlay(CDC *pDC, CComparerDoc *pDoc, ComparerPane *pane)
+{
+	if (!pane || !pane->isAvail() || !pane->rgbBuf)
+		return;
+
+	// Find any other available pane to compare against (pilot assumes 2 panes).
+	ComparerPane *other = nullptr;
+	for (int i = 0; i < CComparerDoc::IMG_VIEW_MAX; i++) {
+		ComparerPane *p = &pDoc->mPane[i];
+		if (p == pane)
+			continue;
+		if (p->isAvail() && p->rgbBuf) {
+			other = p;
+			break;
+		}
+	}
+	if (!other || pDoc->mW <= 0 || pDoc->mH <= 0)
+		return;
+
+	const int rowBytes = ROUNDUP_DWORD(pDoc->mW) * QIMG_DST_RGB_BYTES;
+	const BYTE *bufA = pane->rgbBuf;
+	const BYTE *bufB = other->rgbBuf;
+
+	const int cellPx  = 24;          // grid cell size in display pixels
+	const int dotR    = 3;           // dot radius
+	const COLORREF kPink = RGB(0xff, 0x3d, 0x8a);
+
+	CBrush dotBrush(kPink);
+	CBrush *prevBrush = pDC->SelectObject(&dotBrush);
+	HGDIOBJ prevPen   = pDC->SelectObject(::GetStockObject(NULL_PEN));
+
+	const float invN = (pDoc->mN > 0.0f) ? (1.0f / pDoc->mN) : 1.0f;
+
+	for (int cy = 0; cy < mHCanvas; cy += cellPx) {
+		int cellBot = cy + cellPx;
+		if (cellBot > mHCanvas) cellBot = mHCanvas;
+
+		// Map canvas y range -> source y range.
+		int sy0 = (int)floorf((cy      - mYDst) * invN);
+		int sy1 = (int)ceilf ((cellBot - mYDst) * invN);
+		if (sy0 < 0)         sy0 = 0;
+		if (sy1 > pDoc->mH)  sy1 = pDoc->mH;
+		if (sy0 >= sy1)      continue;
+
+		for (int cx = 0; cx < mWCanvas; cx += cellPx) {
+			int cellRight = cx + cellPx;
+			if (cellRight > mWCanvas) cellRight = mWCanvas;
+
+			int sx0 = (int)floorf((cx        - mXDst) * invN);
+			int sx1 = (int)ceilf ((cellRight - mXDst) * invN);
+			if (sx0 < 0)        sx0 = 0;
+			if (sx1 > pDoc->mW) sx1 = pDoc->mW;
+			if (sx0 >= sx1)     continue;
+
+			// Scan the source rectangle for any differing byte; early exit.
+			bool hasDiff = false;
+			const int byteStart = sx0 * QIMG_DST_RGB_BYTES;
+			const int byteLen   = (sx1 - sx0) * QIMG_DST_RGB_BYTES;
+			for (int sy = sy0; sy < sy1; sy++) {
+				const BYTE *ra = bufA + sy * rowBytes + byteStart;
+				const BYTE *rb = bufB + sy * rowBytes + byteStart;
+				if (memcmp(ra, rb, byteLen) != 0) {
+					hasDiff = true;
+					break;
+				}
+			}
+
+			if (hasDiff) {
+				int dotX = (cx + cellRight) / 2;
+				int dotY = (cy + cellBot)   / 2;
+				pDC->Ellipse(dotX - dotR, dotY - dotR,
+				             dotX + dotR + 1, dotY + dotR + 1);
+			}
+		}
+	}
+
+	pDC->SelectObject(prevBrush);
+	pDC->SelectObject(prevPen);
+}
+
 void CComparerView::DrawEmptyPane(CDC *pDC, CComparerDoc *pDoc)
 {
 	CRect canvas(0, mRcControls.bottom, mWClient, mHClient);

Comparer/ComparerView.h

@@ -57,6 +57,7 @@ class CComparerView : public CScrollView
 	void ScaleNearestNeighbor(CComparerDoc *pDoc, BYTE *src, BYTE *dst, int sDst,
 		q1::GridInfo &gi);
 	void DrawEmptyPane(CDC *pDC, CComparerDoc *pDoc);
+	void DrawDiffOverlay(CDC *pDC, CComparerDoc *pDoc, ComparerPane *pane);
 
 	afx_msg int OnCreate(LPCREATESTRUCT lpCreateStruct);
 	afx_msg void OnDropFiles(HDROP hDropInfo);

Comparer/PosInfoView.cpp

@@ -59,21 +59,6 @@ void CPosInfoView::OnInitialUpdate()
 	CScrollView::OnInitialUpdate();
 }
 
-static void DrawDiffPosLines(CDC *pDC, CRect *frameRect, bool *flags, int n)
-{
-	int top = frameRect->top + 1;
-	int left = frameRect->left + 1;
-	int right = frameRect->right - 1;
-
-	for (int i = 0; i < n; i++) {
-		if (flags[i] == false)
-			continue;
-
-		pDC->MoveTo(left, top + i);
-		pDC->LineTo(right, top + i);
-	}
-}
-
 void CPosInfoView::DrawEachRect(CDC* pDC,
 								ComparerPane *pane,
 								CRect *frameRect,
@@ -98,17 +83,9 @@ void CPosInfoView::DrawEachRect(CDC* pDC,
 	pDC->FillSolidRect(frameRect, frameColor);
 	pDC->Draw3dRect(frameRect, Q1UI_COLOR_SURFACE, Q1UI_COLOR_SURFACE);
 
-	if (parseDone) {
-		CPen *prev = pDC->SelectObject(mDiffPen);
-		IFrmCmpStrategy *frmCmpStrategy = pDoc->mFrmCmpStrategy;
-		list<RLC> diffRLC[QPLANES];
-
-		if (mFileScanThread->copyDiffRLC(i, diffRLC)) {
-			frmCmpStrategy->FlagTotalDiffLine(diffRLC, mDiffFlags, mPosLinesPerFrame);
-			DrawDiffPosLines(pDC, frameRect, mDiffFlags, mPosLinesPerFrame);
-		}
-		pDC->SelectObject(prev);
-	}
+	// Per-row red diff lines have been replaced by the pink grid overlay in
+	// ComparerView. Pilot keeps the frame tiles for video-frame selection but
+	// no longer draws the per-row indicators.
 
 	const COLORREF curIdColor = Q1UI_COLOR_ACCENT;
 	COLORREF preColor;
@@ -183,7 +160,13 @@ void CPosInfoView::OnDraw(CDC* pDC)
 
 	memDC.FillSolidRect(CRect(0, 0, mWClient, h), Q1UI_COLOR_APP_BG);
 
-	if (!paneL->isAvail() && !paneR->isAvail()) {
+	// Pilot: hide the timeline entirely when neither pane is a video. The pink
+	// grid overlay in ComparerView already conveys diff information; the
+	// timeline is only useful for picking a frame in a video source.
+	bool hasVideo = (paneL->isAvail() && paneL->frames > 1)
+	             || (paneR->isAvail() && paneR->frames > 1);
+
+	if (!paneL->isAvail() && !paneR->isAvail() || !hasVideo) {
 		LOGFONT lf;
 		mPosNumFont.GetLogFont(&lf);
 		::lstrcpy(lf.lfFaceName, Q1UI_FONT_TEXT);
@@ -195,7 +178,10 @@ void CPosInfoView::OnDraw(CDC* pDC)
 		memDC.SetBkMode(TRANSPARENT);
 		memDC.SetTextColor(Q1UI_COLOR_TEXT_MUTED);
 		CRect msgRect(0, 0, mWClient, h);
-		memDC.DrawText(_T("Timeline"), &msgRect, DT_SINGLELINE | DT_CENTER | DT_VCENTER);
+		LPCTSTR msg = (paneL->isAvail() || paneR->isAvail())
+			? _T("Timeline\n(video only)") : _T("Timeline");
+		memDC.DrawText(msg, &msgRect,
+			DT_CENTER | DT_VCENTER | DT_WORDBREAK | DT_NOCLIP);
 		memDC.SelectObject(prevFont);
 		goto OnDrawExit;
 	}