Implement continuous scrolling

2026-03-01 10:22:58 -05:00 · 2026-02-22 19:28:37 +01:00
parent 2450c94972
commit adfa058742
17 changed files with 848 additions and 39 deletions
--- a/YACReader/continuous_page_widget.h
+++ b/YACReader/continuous_page_widget.h
@ -0,0 +1,86 @@
+#ifndef CONTINUOUS_PAGE_WIDGET_H
+#define CONTINUOUS_PAGE_WIDGET_H
+
+#include <QWidget>
+#include <QSize>
+#include <QVector>
+
+#include "themable.h"
+
+class Render;
+
+class ContinuousPageWidget : public QWidget, protected Themable
+{
+    Q_OBJECT
+public:
+    explicit ContinuousPageWidget(QWidget *parent = nullptr);
+
+    void setRender(Render *r);
+    void setNumPages(int count);
+    void setZoomFactor(int zoom);
+    void probeBufferedPages();
+    void reset();
+
+    int centerPage(int scrollY, int viewportHeight) const;
+    int yPositionForPage(int pageIndex) const;
+    int totalHeight() const;
+
+    bool hasHeightForWidth() const override;
+    int heightForWidth(int w) const override;
+    QSize sizeHint() const override;
+
+    void setAnchorPage(int page);
+    void setViewportState(int scrollY, int viewportHeight);
+
+signals:
+    // emitted after layout recomputation when the preserved viewport anchor
+    // resolves to an absolute scroll position
+    void layoutScrollPositionRequested(int scrollY);
+
+public slots:
+    void onPageAvailable(int absolutePageIndex);
+
+protected:
+    void paintEvent(QPaintEvent *event) override;
+    void resizeEvent(QResizeEvent *event) override;
+    void applyTheme(const Theme &theme) override;
+
+private:
+    struct LayoutSnapshot {
+        QVector<int> yPositions;
+        QVector<QSize> scaledSizes;
+        int totalHeight = 0;
+    };
+
+    struct ViewportAnchor {
+        int pageIndex = -1;
+        float offsetRatio = 0.0f;
+        bool valid = false;
+    };
+
+    void updateLayout();
+    void updateLayoutWithAnchor();
+    void relayout(bool preserveAnchor);
+    LayoutSnapshot buildLayoutSnapshot(int w) const;
+    int pageAtY(const LayoutSnapshot &snapshot, int y) const;
+    ViewportAnchor anchorFromViewport(const LayoutSnapshot &snapshot, int scrollY, int viewportHeight) const;
+    int resolveAnchorToScrollY(const LayoutSnapshot &snapshot, const ViewportAnchor &anchor, int viewportHeight) const;
+    int pageAtY(int y) const;
+    QSize scaledPageSize(int pageIndex, int forWidth) const;
+    float scaleForPage(int pageIndex, int forWidth) const;
+
+    Render *render = nullptr;
+    int numPages = 0;
+    QVector<QSize> pageSizes;
+    QVector<int> yPositions;
+    int currentTotalHeight = 0;
+    LayoutSnapshot layoutSnapshot;
+    QSize defaultPageSize { 800, 1200 };
+    int zoomFactor = 100;
+    int anchorPage = -1;
+    int viewportScrollY = 0;
+    int currentViewportHeight = 0;
+    bool hasViewportState = false;
+};
+
+#endif // CONTINUOUS_PAGE_WIDGET_H