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[UnifiedPDF] Implement two-up display mode
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https://bugs.webkit.org/show_bug.cgi?id=262454
rdar://116296737

Reviewed by Dan Glastonbury.

Implement two-up display mode, which displays pairs of pages side-by-side.

In this mode, the height of the pair of pages is the larger of the two heights, and pages with
unequal heights are vertically centered in the row. If there is a single page on the last row, it's
centered (which is also the case for a single page PDF).

Have `PDFDocumentLayout::updateLayout()` keep track of the width of page pairs when necessary, which
is passed to `layoutTwoUpColumn()`.

* Source/WebKit/WebProcess/Plugins/PDF/UnifiedPDF/PDFDocumentLayout.h:
* Source/WebKit/WebProcess/Plugins/PDF/UnifiedPDF/PDFDocumentLayout.mm:
(WebKit::PDFDocumentLayout::updateLayout):
(WebKit::PDFDocumentLayout::layoutPages):
(WebKit::PDFDocumentLayout::layoutSingleColumn):
(WebKit::PDFDocumentLayout::layoutTwoUpColumn):

Canonical link: https://commits.webkit.org/268733@main
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@smfr
smfr committed Oct 2, 2023
1 parent 3f6e793 commit 808bcd5
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Showing 2 changed files with 87 additions and 18 deletions.
6 changes: 3 additions & 3 deletions Source/WebKit/WebProcess/Plugins/PDF/UnifiedPDF/PDFDocumentLayout.h
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Original file line number Diff line number Diff line change
Expand Up @@ -71,10 +71,10 @@ class PDFDocumentLayout {
WebCore::FloatSize scaledContentsSize() const;

private:
void layoutPages(float availableWidth, float maxPageWidth);
void layoutPages(float availableWidth, float maxRowWidth);

void layoutSingleColumn(float availableWidth, float maxPageWidth);
void layoutTwoUpColumn(float availableWidth);
void layoutSingleColumn(float availableWidth, float maxRowWidth);
void layoutTwoUpColumn(float availableWidth, float maxRowWidth);

static FloatSize documentMargin();
static FloatSize pageMargin();
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99 changes: 84 additions & 15 deletions Source/WebKit/WebProcess/Plugins/PDF/UnifiedPDF/PDFDocumentLayout.mm
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Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,8 @@
namespace WebKit {
using namespace WebCore;

static constexpr float minScale = 0.1; // Arbitrarily chosen min scale.

FloatSize PDFDocumentLayout::documentMargin()
{
return { 20, 20 };
Expand Down Expand Up @@ -88,7 +90,11 @@
return r;
};

float maxPageWidth = 0;
float maxRowWidth = 0;
float currentRowWidth = 0;
bool isTwoUpLayout = m_displayMode == DisplayMode::TwoUp || m_displayMode == DisplayMode::TwoUpContinuous;

auto pageMargin = PDFDocumentLayout::pageMargin();

for (PageIndex i = 0; i < pageCount; ++i) {
auto page = pageAtIndex(i);
Expand All @@ -103,68 +109,131 @@
LOG_WITH_STREAM(Plugins, stream << "PDFDocumentLayout::updateLayout() - page " << i << " crop box " << pageCropBox << " rotation " << rotation);

auto pageBounds = normalizePageBounds(pageCropBox, rotation);
maxPageWidth = std::max(maxPageWidth, pageBounds.width());

if (isTwoUpLayout) {
if (i % 2) {
currentRowWidth += pageMargin.width() + pageBounds.width();
maxRowWidth = std::max(maxRowWidth, currentRowWidth);
} else {
currentRowWidth = pageBounds.width();
if (i == pageCount - 1)
maxRowWidth = std::max(maxRowWidth, currentRowWidth);
}
} else
maxRowWidth = std::max(maxRowWidth, pageBounds.width());

m_pageGeometry.append({ pageBounds, rotation });
}

layoutPages(pluginSize.width(), maxPageWidth);
auto documentMargin = PDFDocumentLayout::documentMargin();
maxRowWidth += 2 * documentMargin.width();

layoutPages(pluginSize.width(), maxRowWidth);

LOG_WITH_STREAM(Plugins, stream << "PDFDocumentLayout::updateLayout() - plugin size " << pluginSize << " document bounds " << m_documentBounds << " scale " << m_scale);
}

void PDFDocumentLayout::layoutPages(float availableWidth, float maxPageWidth)
void PDFDocumentLayout::layoutPages(float availableWidth, float maxRowWidth)
{
// We always lay out in a continuous mode. We handle non-continuous mode via scroll snap.
switch (m_displayMode) {
case DisplayMode::SinglePage:
case DisplayMode::Continuous:
layoutSingleColumn(availableWidth, maxPageWidth);
layoutSingleColumn(availableWidth, maxRowWidth);
break;

case DisplayMode::TwoUp:
case DisplayMode::TwoUpContinuous:
layoutTwoUpColumn(availableWidth);
layoutTwoUpColumn(availableWidth, maxRowWidth);
break;
}
}

void PDFDocumentLayout::layoutSingleColumn(float availableWidth, float maxPageWidth)
void PDFDocumentLayout::layoutSingleColumn(float availableWidth, float maxRowWidth)
{
auto documentMargin = PDFDocumentLayout::documentMargin();
auto pageMargin = PDFDocumentLayout::pageMargin();

float currentYOffset = documentMargin.height();
auto pageCount = this->pageCount();

maxPageWidth += 2 * documentMargin.width();

for (PageIndex i = 0; i < pageCount; ++i) {
if (i >= m_pageGeometry.size())
break;

auto pageBounds = m_pageGeometry[i].normalizedBounds;

auto pageLeft = std::max<float>(std::floor((maxPageWidth - pageBounds.width()) / 2), 0);
auto pageLeft = std::max<float>(std::floor((maxRowWidth - pageBounds.width()) / 2), 0);
pageBounds.setLocation({ pageLeft, currentYOffset });

currentYOffset += pageBounds.height() + pageMargin.height();

m_pageGeometry[i].normalizedBounds = pageBounds;
}

// Subtract the last page's bottom margin.
currentYOffset -= pageMargin.height();
currentYOffset += documentMargin.height();

constexpr float minScale = 0.1; // Arbitrarily chosen min scale.
m_scale = std::max<float>(availableWidth / maxPageWidth, minScale);
m_scale = std::max<float>(availableWidth / maxRowWidth, minScale);
m_documentBounds = FloatRect { 0, 0, availableWidth, currentYOffset };
}

void PDFDocumentLayout::layoutTwoUpColumn(float availableWidth)
void PDFDocumentLayout::layoutTwoUpColumn(float availableWidth, float maxRowWidth)
{
// FIMXE: Not implemented yet.
auto documentMargin = PDFDocumentLayout::documentMargin();
auto pageMargin = PDFDocumentLayout::pageMargin();

FloatSize currentRowSize;
float currentYOffset = documentMargin.height();
auto pageCount = this->pageCount();

for (PageIndex i = 0; i < pageCount; ++i) {
if (i >= m_pageGeometry.size())
break;

auto pageBounds = m_pageGeometry[i].normalizedBounds;

// Lay out the pages in pairs.
if (i % 2) {
currentRowSize.expand(pageMargin.width() + pageBounds.width(), 0);
currentRowSize.setHeight(std::max(currentRowSize.height(), pageBounds.height()));

auto leftPageBounds = m_pageGeometry[i - 1].normalizedBounds;
auto rightPageBounds = pageBounds;

// Center each page vertically in the row.
// Center the pair of pages horizontally.
float horizontalSpace = maxRowWidth - 2 * documentMargin.width() - leftPageBounds.width() - rightPageBounds.width();
leftPageBounds.setX(std::floor(documentMargin.width() + horizontalSpace / 2));
rightPageBounds.setX(leftPageBounds.maxX() + pageMargin.width());

float leftVerticalSpace = currentRowSize.height() - leftPageBounds.height();
leftPageBounds.setY(currentYOffset + std::floor(leftVerticalSpace / 2));

float rightVerticalSpace = currentRowSize.height() - rightPageBounds.height();
rightPageBounds.setY(currentYOffset + std::floor(rightVerticalSpace / 2));

m_pageGeometry[i - 1].normalizedBounds = leftPageBounds;
m_pageGeometry[i].normalizedBounds = rightPageBounds;

currentYOffset += currentRowSize.height() + pageMargin.height();
} else {
currentRowSize = pageBounds.size();
if (i == pageCount - 1) {
// Position the last page, which is centered horizontally.
float horizontalSpace = maxRowWidth - 2 * documentMargin.width() - pageBounds.width();
m_pageGeometry[i].normalizedBounds.setLocation({ documentMargin.width() + std::floor(horizontalSpace / 2), currentYOffset });
currentYOffset += currentRowSize.height() + pageMargin.height();
}
}
}

// Subtract the last row's bottom margin.
currentYOffset -= pageMargin.height();
currentYOffset += documentMargin.height();

m_scale = std::max<float>(availableWidth / maxRowWidth, minScale);
m_documentBounds = FloatRect { 0, 0, availableWidth, currentYOffset };
}

size_t PDFDocumentLayout::pageCount() const
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