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Change the WinIMergeLib splitter position API to use splitter ratios instead of absolute positions. #40

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Merged
sdottaka merged 6 commits into from
Sep 4, 2026
Merged

Change the WinIMergeLib splitter position API to use splitter ratios instead of absolute positions. #40

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9e64d70
Change the WinIMergeLib splitter position API to use splitter ratios …
sdottaka Sep 3, 2026
5b8a6f4
Change the WinIMergeLib splitter position API to use splitter ratios …
sdottaka Sep 4, 2026
627a5e9
Change the WinIMergeLib splitter position API to use splitter ratios …
sdottaka Sep 4, 2026
97b0961
Change the WinIMergeLib splitter position API to use splitter ratios …
sdottaka Sep 4, 2026
10bfbe1
Change the WinIMergeLib splitter position API to use splitter ratios …
sdottaka Sep 4, 2026
0c7ccb7
Change the WinIMergeLib splitter position API to use splitter ratios …
sdottaka Sep 4, 2026
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247 changes: 137 additions & 110 deletions src/WinIMergeLib/ImgMergeWindow.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -64,7 +64,6 @@ 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 All @@ -75,10 +74,10 @@ class CImgMergeWindow : public IImgMergeWindow
, m_gdiplusToken(0)
, m_timerPrev()
, m_timerNext()
, m_splitterRatios{ -1.0, -1.0 }
, m_requestedSplitterRatios{ -1.0, -1.0 }
, m_ChildWndProc{ nullptr, nullptr, nullptr }
{
for (int i = 0; i < 3; ++i)
m_ChildWndProc[i] = NULL;

Gdiplus::GdiplusStartupInput gdiplusStartupInput;
Gdiplus::GdiplusStartup(&m_gdiplusToken, &gdiplusStartupInput, nullptr);
}
Expand Down Expand Up @@ -215,11 +214,8 @@ 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);
std::vector<RECT> rects = CalcChildImgWindowRect(m_hWnd, m_nImages, m_bHorizontalSplit, m_splitterRatios);
for (int i = 0; i < m_nImages; ++i)
{
if (i < m_nImages - 1)
Expand All @@ -228,22 +224,38 @@ class CImgMergeWindow : public IImgMergeWindow
}
}

int GetSplitterPosition() const override
double GetSplitterRatio(int pane) const override
{
return m_splitterPosition;
if (pane < 0 || pane >= std::size(m_splitterRatios))
return -1.0;
return m_splitterRatios[pane];
}
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sdottaka marked this conversation as resolved.

void SetSplitterPosition(int position) override
void SetSplitterRatios(const double* ratios, int count) 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)
if (count > std::size(m_splitterRatios) || !ratios || count < 1)
return;
for (int i = 0; i < count; ++i)
Comment thread
sdottaka marked this conversation as resolved.
{
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]);
if (ratios[i] >= 0.0 && ratios[i] <= 1.0)
{
m_splitterRatios[i] = ratios[i];
m_requestedSplitterRatios[i] = ratios[i];
}
}
ApplySplitterRatio();
}

void ResetSplitterRatios() override
{
if (m_nImages < 2)
return;
for (int i = 0; i < m_nImages - 1; ++i)
{
m_splitterRatios[i] = 1.0 / m_nImages;
m_requestedSplitterRatios[i] = -1.0;
}
ApplySplitterRatio();
}

COLORREF GetDiffColor() const override
Expand Down Expand Up @@ -880,6 +892,8 @@ class CImgMergeWindow : public IImgMergeWindow
{
CloseImages();
m_nImages = nImages;
for (int i = 0; i < nImages - 1; ++i)
m_splitterRatios[i] = (m_requestedSplitterRatios[i] < 0.0) ? 1.0 / nImages : m_requestedSplitterRatios[i];
bool bSucceeded = m_buffer.NewImages(nImages, nPages, width, height);
if (m_hWnd)
{
Expand All @@ -892,7 +906,7 @@ class CImgMergeWindow : public IImgMergeWindow
m_buffer.CompareImages();
if (m_hWnd)
{
std::vector<RECT> rects = CalcChildImgWindowRect(m_hWnd, nImages, m_bHorizontalSplit);
std::vector<RECT> rects = CalcChildImgWindowRect(m_hWnd, nImages, m_bHorizontalSplit, m_splitterRatios);
for (int i = 0; i < nImages; ++i)
{
if (i < nImages - 1)
Expand All @@ -913,6 +927,8 @@ class CImgMergeWindow : public IImgMergeWindow
{
CloseImages();
m_nImages = nImages;
for (int i = 0; i < nImages - 1; ++i)
m_splitterRatios[i] = (m_requestedSplitterRatios[i] < 0.0) ? 1.0 / nImages : m_requestedSplitterRatios[i];
bool bSucceeded = m_buffer.OpenImages(nImages, filename);
if (m_hWnd)
{
Expand All @@ -925,7 +941,7 @@ class CImgMergeWindow : public IImgMergeWindow
m_buffer.CompareImages();
if (m_hWnd)
{
std::vector<RECT> rects = CalcChildImgWindowRect(m_hWnd, nImages, m_bHorizontalSplit);
std::vector<RECT> rects = CalcChildImgWindowRect(m_hWnd, nImages, m_bHorizontalSplit, m_splitterRatios);
for (int i = 0; i < nImages; ++i)
{
if (i < nImages - 1)
Expand Down Expand Up @@ -1283,95 +1299,85 @@ 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> CalcChildImgWindowRect(HWND hWnd, int nImages, bool bHorizontalSplit, const double* ratios = nullptr)
{
std::vector<RECT> childrects;
std::vector<RECT> rects;
RECT rcParent;
GetClientRect(hWnd, &rcParent);
RECT rc = rcParent;
if (nImages > 0)

if (nImages < 1)
return rects;

rects.resize(nImages);

if (!bHorizontalSplit)
{
if (!bHorizontalSplit)
// Vertical split
int cx = GetSystemMetrics(SM_CXVSCROLL);
int totalWidth = rcParent.right - rcParent.left - cx;
int accumulatedWidth = 0;

// Ratio-based division
for (int i = 0; i < nImages; ++i)
{
const int splitPos = CalcSplitterPosition(nImages, rcParent.right);
if (splitPos > 0)
rects[i].top = rcParent.top;
rects[i].bottom = rcParent.bottom;

if (i < nImages - 1)
{
rc.left = 0;
rc.right = splitPos;
childrects.push_back(rc);
rc.left = rc.right + 2 * 2;
rc.right = rcParent.right;
childrects.push_back(rc);
int paneWidth = static_cast<int>(totalWidth * ratios[i]);
rects[i].left = accumulatedWidth;
rects[i].right = accumulatedWidth + paneWidth;
accumulatedWidth = rects[i].right + 4; // 4 pixels for splitter
}
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);
// Last pane takes remaining width
rects[i].left = accumulatedWidth;
rects[i].right = rcParent.right;
}
}
else
}
else
{
// Horizontal split
int cy = GetSystemMetrics(SM_CXVSCROLL);
int totalHeight = rcParent.bottom - rcParent.top - cy;
int accumulatedHeight = 0;

// Ratio-based division
for (int i = 0; i < nImages; ++i)
{
const int splitPos = CalcSplitterPosition(nImages, rcParent.bottom);
if (splitPos > 0)
rects[i].left = rcParent.left;
rects[i].right = rcParent.right;

if (i < nImages - 1)
{
rc.top = 0;
rc.bottom = splitPos;
childrects.push_back(rc);
rc.top = rc.bottom + 2 * 2;
rc.bottom = rcParent.bottom;
childrects.push_back(rc);
int paneHeight = static_cast<int>(totalHeight * ratios[i]);
rects[i].top = accumulatedHeight;
rects[i].bottom = accumulatedHeight + paneHeight;
accumulatedHeight = rects[i].bottom + 4; // 4 pixels for splitter
}
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);
// Last pane takes remaining height
rects[i].top = accumulatedHeight;
rects[i].bottom = rcParent.bottom;
}
}
}
return childrects;

return rects;
}

void ApplySplitterRatio()
{
if (!m_hWnd || m_nImages < 2)
return;

std::vector<RECT> rects = CalcChildImgWindowRect(m_hWnd, m_nImages, m_bHorizontalSplit, m_splitterRatios);
for (int i = 0; i < m_nImages; ++i)
m_imgWindow[i].SetWindowRect(rects[i]);
}

void MoveSplitter(int x, int y)
Expand Down Expand Up @@ -1421,23 +1427,47 @@ 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)
for (int i = 0; i < m_nImages; ++i)
m_imgWindow[i].SetWindowRect(rc[i]);

// Update ratios based on new positions
UpdateSplitterRatios();
}

void UpdateSplitterRatios()
{
if (m_nImages < 2)
return;

RECT rcParent;
GetClientRect(m_hWnd, &rcParent);

if (!m_bHorizontalSplit)
{
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;
// Vertical split: calculate width ratios
int cx = GetSystemMetrics(SM_CXVSCROLL);
int totalWidth = rcParent.right - rcParent.left - cx;

for (int i = 0; i < m_nImages - 1; ++i)
{
RECT paneRc = m_imgWindow[i].GetWindowRect();
int paneWidth = paneRc.right - paneRc.left;
m_splitterRatios[i] = static_cast<double>(paneWidth) / totalWidth;
}
}
else
{
// Horizontal split: calculate height ratios
int cy = GetSystemMetrics(SM_CXVSCROLL);
int totalHeight = rcParent.bottom - rcParent.top - cy;

for (int i = 0; i < m_nImages; ++i)
m_imgWindow[i].SetWindowRect(rc[i]);
for (int i = 0; i < m_nImages - 1; ++i)
{
RECT paneRc = m_imgWindow[i].GetWindowRect();
int paneHeight = paneRc.bottom - paneRc.top;
m_splitterRatios[i] = static_cast<double>(paneHeight) / totalHeight;
}
}
}

void DrawXorBar(HDC hdc, int x1, int y1, int width, int height)
Expand Down Expand Up @@ -1489,9 +1519,7 @@ class CImgMergeWindow : public IImgMergeWindow

void OnSize(UINT nType, int cx, int cy)
{
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]);
ApplySplitterRatio();
}

void OnKeyDown(UINT nChar, UINT nRepCnt, UINT nFlags)
Expand Down Expand Up @@ -2126,9 +2154,6 @@ 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 All @@ -2141,5 +2166,7 @@ class CImgMergeWindow : public IImgMergeWindow
std::unique_ptr<ocr::COcr> m_pOcr;
std::chrono::milliseconds m_timerPrev;
std::chrono::milliseconds m_timerNext;
double m_requestedSplitterRatios[2];
double m_splitterRatios[2];
inline static bool s_bDarkBackgroundEnabled = false;
};
5 changes: 3 additions & 2 deletions src/WinIMergeLib/WinIMergeLib.h
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Original file line number Diff line number Diff line change
Expand Up @@ -192,8 +192,9 @@ 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;
virtual double GetSplitterRatio(int pane) const = 0;
virtual void SetSplitterRatios(const double* ratios, int count) = 0;
virtual void ResetSplitterRatios() = 0;
};

struct IImgToolWindow
Expand Down
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