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Remember the splitter position in image compare #39

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Merged
sdottaka merged 1 commit into from
Aug 30, 2026
Merged

Remember the splitter position in image compare #39

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119 changes: 103 additions & 16 deletions src/WinIMergeLib/ImgMergeWindow.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -64,6 +64,7 @@ class CImgMergeWindow : public IImgMergeWindow
, m_hInstance(NULL)
, m_nDraggingSplitter(-1)
, m_bHorizontalSplit(false)
, m_splitterPosition(0)
, m_oldSplitPosX(-4)
, m_oldSplitPosY(-4)
, m_bDragging(false)
Expand Down Expand Up @@ -214,6 +215,9 @@ class CImgMergeWindow : public IImgMergeWindow
{
if (!m_hWnd)
return;
// A stored width cannot be reused as a height.
if (m_bHorizontalSplit != horizontalSplit)
m_splitterPosition = 0;
m_bHorizontalSplit = horizontalSplit;
std::vector<RECT> rects = CalcChildImgWindowRect(m_hWnd, m_nImages, m_bHorizontalSplit);
for (int i = 0; i < m_nImages; ++i)
Expand All @@ -224,6 +228,24 @@ class CImgMergeWindow : public IImgMergeWindow
}
}

int GetSplitterPosition() const override
{
return m_splitterPosition;
}

void SetSplitterPosition(int position) override
{
// Stored before the window check: unlike SetHorizontalSplit(), a value
// set before the panes exist must survive until they are created.
m_splitterPosition = position;
if (m_hWnd && m_nImages == 2)
{
std::vector<RECT> rects = CalcChildImgWindowRect(m_hWnd, m_nImages, m_bHorizontalSplit);
for (int i = 0; i < m_nImages; ++i)
m_imgWindow[i].SetWindowRect(rects[i]);
}
}

COLORREF GetDiffColor() const override
{
return RGBQUADtoCOLORREF(m_buffer.GetDiffColor());
Expand Down Expand Up @@ -1261,6 +1283,27 @@ class CImgMergeWindow : public IImgMergeWindow
return RegisterClassExW(&wcex);
}

// First pane size to lay out, or 0 for the equal split. A positive
// m_splitterPosition sizes the first pane from the near edge, a negative one
// sizes the second pane from the far edge; whichever pane is smaller is the
// anchored one, so a narrow pane stays narrow and the wide pane absorbs the
// window change. Bounds match the ones MoveSplitter() enforces, so a
// restored layout matches the dragged one. The clamp is returned, never
// stored back: the window is laid out once before it has its final size, and
// clamping in place would let that transient rect shrink the value for good.
int CalcSplitterPosition(int nImages, LONG splitSize) const
{
const int minSize = 32;
const int total = static_cast<int>(splitSize);
const int maxPos = total - minSize;
if (nImages != 2 || m_splitterPosition == 0 || maxPos < minSize)
return 0;
const int pos = (m_splitterPosition > 0)
? m_splitterPosition
: total - 2 * 2 + m_splitterPosition;
return (std::min)((std::max)(pos, minSize), maxPos);
}

std::vector<RECT> CalcChildImgWindowRect(HWND hWnd, int nImages, bool bHorizontalSplit)
{
std::vector<RECT> childrects;
Expand All @@ -1271,35 +1314,61 @@ class CImgMergeWindow : public IImgMergeWindow
{
if (!bHorizontalSplit)
{
int cx = GetSystemMetrics(SM_CXVSCROLL);
int width = (rcParent.left + rcParent.right - cx) / nImages - 2;
rc.left = 0;
rc.right = rc.left + width;
for (int i = 0; i < nImages - 1; ++i)
const int splitPos = CalcSplitterPosition(nImages, rcParent.right);
if (splitPos > 0)
{
rc.left = 0;
rc.right = splitPos;
childrects.push_back(rc);
rc.left = rc.right + 2 * 2;
rc.right = rcParent.right;
childrects.push_back(rc);
}
else
{
int cx = GetSystemMetrics(SM_CXVSCROLL);
int width = (rcParent.left + rcParent.right - cx) / nImages - 2;
rc.left = 0;
rc.right = rc.left + width;
for (int i = 0; i < nImages - 1; ++i)
{
childrects.push_back(rc);
rc.left = rc.right + 2 * 2;
rc.right = rc.left + width;
}
rc.right = rcParent.right;
rc.left = rc.right - width - cx;
childrects.push_back(rc);
}
rc.right = rcParent.right;
rc.left = rc.right - width - cx;
childrects.push_back(rc);
}
else
{
int cy = GetSystemMetrics(SM_CXVSCROLL);
int height = (rcParent.top + rcParent.bottom - cy) / nImages - 2;
rc.top = 0;
rc.bottom = rc.top + height;
for (int i = 0; i < nImages - 1; ++i)
const int splitPos = CalcSplitterPosition(nImages, rcParent.bottom);
if (splitPos > 0)
{
rc.top = 0;
rc.bottom = splitPos;
childrects.push_back(rc);
rc.top = rc.bottom + 2 * 2;
rc.bottom = rcParent.bottom;
childrects.push_back(rc);
}
else
{
int cy = GetSystemMetrics(SM_CXVSCROLL);
int height = (rcParent.top + rcParent.bottom - cy) / nImages - 2;
rc.top = 0;
rc.bottom = rc.top + height;
for (int i = 0; i < nImages - 1; ++i)
{
childrects.push_back(rc);
rc.top = rc.bottom + 2 * 2;
rc.bottom = rc.top + height;
}
rc.bottom = rcParent.bottom;
rc.top = rc.bottom - height - cy;
childrects.push_back(rc);
}
rc.bottom = rcParent.bottom;
rc.top = rc.bottom - height - cy;
childrects.push_back(rc);
}
}
return childrects;
Expand Down Expand Up @@ -1352,6 +1421,21 @@ class CImgMergeWindow : public IImgMergeWindow
rc[m_nImages - 1].bottom = rcParent.bottom;
}

// Recorded after the clamping above, so the stored value is always a
// position the layout can reproduce. OnLButtonUp() clears
// m_nDraggingSplitter only once this returns. The smaller pane is the one
// pinned to its edge, negated when that is the second pane.
if (m_nImages == 2 && m_nDraggingSplitter == 0)
{
const int first = m_bHorizontalSplit
? rc[0].bottom - rc[0].top
: rc[0].right - rc[0].left;
const int second = m_bHorizontalSplit
? rc[1].bottom - rc[1].top
: rc[1].right - rc[1].left;
m_splitterPosition = (second < first) ? -second : first;
}

for (int i = 0; i < m_nImages; ++i)
m_imgWindow[i].SetWindowRect(rc[i]);
}
Expand Down Expand Up @@ -2042,6 +2126,9 @@ class CImgMergeWindow : public IImgMergeWindow
std::vector<EventListenerInfo> m_listener;
int m_nDraggingSplitter;
bool m_bHorizontalSplit;
// Size along the split axis of whichever pane is smaller, in pixels:
// positive for the first pane, negative for the second. 0 = equal split.
int m_splitterPosition;
int m_oldSplitPosX;
int m_oldSplitPosY;
bool m_bDragging;
Expand Down
2 changes: 2 additions & 0 deletions src/WinIMergeLib/WinIMergeLib.h
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Original file line number Diff line number Diff line change
Expand Up @@ -192,6 +192,8 @@ struct IImgMergeWindow
virtual int GetLastErrorCode() const = 0;
virtual bool GetPreferWICDecoder() const = 0;
virtual void SetPreferWICDecoder(bool preferWICDecoder) = 0;
virtual int GetSplitterPosition() const = 0;
virtual void SetSplitterPosition(int position) = 0;
};

struct IImgToolWindow
Expand Down