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ZepDisplay_Qt is the Qt rendering backend for Zep. It implements the ZepDisplay interface using Qt’s QPainter API. Header: include/zep/qt/zepdisplay_qt.h

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Classes

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ZepDisplay_Qt

Qt implementation of the display interface. 
class ZepDisplay_Qt : public ZepDisplay
{
public:
    ZepDisplay_Qt();
    ~ZepDisplay_Qt();
    
    void SetPainter(QPainter* pPainter);
    
    // ZepDisplay interface implementation
    void DrawChars(ZepFont& font, const NVec2f& pos, const NVec4f& col,
                   const uint8_t* text_begin, const uint8_t* text_end) const override;
    void DrawLine(const NVec2f& start, const NVec2f& end,
                  const NVec4f& color, float width) const override;
    void DrawRectFilled(const NRectf& rc, const NVec4f& color) const override;
    void SetClipRect(const NRectf& rc) override;
    ZepFont& GetFont(ZepTextType type) override;
};

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ZepFont_Qt

Qt font wrapper using QFont. 
class ZepFont_Qt : public ZepFont
{
public:
    ZepFont_Qt(ZepDisplay& display, const std::string& filePath, int pixelHeight);
    
    void SetPixelHeight(int val) override;
    NVec2f GetTextSize(const uint8_t* pBegin,
                       const uint8_t* pEnd = nullptr) const override;
    QFont& GetQtFont();
    float Descent() const;
};

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Implementation Details

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Painter Management (zepdisplay_qt.h:111)

void SetPainter(QPainter* pPainter);
You must call this before any drawing operations to set the active QPainter instance. Typically called at the start of your widget’s paintEvent().

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Drawing Operations

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DrawChars (zepdisplay_qt.h:116)

void DrawChars(ZepFont& font, const NVec2f& pos, const NVec4f& col,
               const uint8_t* text_begin, const uint8_t* text_end) const override;
  • Casts font to ZepFont_Qt and applies it via QPainter::setFont()
  • Sets pen color using QColor::fromRgbF()
  • Uses QPainter::drawText() with Qt::TextLongestVariant flag
  • Adjusts vertical position to account for font descent
  • Text is rendered as UTF-8 using QString::fromUtf8()

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DrawLine (zepdisplay_qt.h:133)

void DrawLine(const NVec2f& start, const NVec2f& end,
              const NVec4f& color, float width) const override;
  • Uses QPainter::drawLine() with a QPen of specified width and color
  • Color is converted to QColor via QColor::fromRgbF()

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DrawRectFilled (zepdisplay_qt.h:141)

void DrawRectFilled(const NRectf& rc, const NVec4f& color) const override;
  • Uses QPainter::fillRect() with a QRect and QColor
  • Converts Zep’s rect format to Qt’s QRect

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Clipping (zepdisplay_qt.h:148)

void SetClipRect(const NRectf& rc) override;
  • Sets clip rect via QPainter::setClipRect() if width > 0
  • Disables clipping with QPainter::setClipping(false) when width is 0
  • Stores the current clip rect in m_clipRect

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Font Management (zepdisplay_qt.h:162)

ZepFont& GetFont(ZepTextType type) override;
  • Creates ZepFont_Qt instances on demand
  • Uses application default font height as base
  • Scales font size for heading types:
    • Heading1: 1.75x base height
    • Heading2: 1.5x base height
    • Heading3: 1.25x base height

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Font Configuration (zepdisplay_qt.h:40)

ZepFont_Qt::SetPixelHeight() configures the font:
  • Uses "Menlo" on macOS, "Consolas" on other platforms
  • Sets QFont::Monospace style hint
  • Calculates and caches font descent using QFontMetrics
  • Invalidates character size cache

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Text Measurement (zepdisplay_qt.h:57)

NVec2f GetTextSize(const uint8_t* pBegin, const uint8_t* pEnd = nullptr) const override;
  • Uses QFontMetrics::size() with flags:
    • Qt::TextIncludeTrailingSpaces
    • Qt::TextLongestVariant
  • Handles tab characters by multiplying width by 4
  • Falls back to ‘A’ character size for invalid glyphs
  • Returns width and height as NVec2f

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Helper Functions

The header provides conversion utilities: 
inline NVec2f toNVec2f(const QPoint& im);
inline NVec2f toNVec2f(const QPointF& im);
inline QPoint toQPoint(const NVec2f& im);

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Usage Example

#include "zep/qt/zepdisplay_qt.h"
#include "zep/editor.h"
#include <QWidget>
#include <QPainter>

class ZepWidget : public QWidget {
public:
    ZepWidget(QWidget* parent = nullptr)
        : QWidget(parent),
          m_display(std::make_shared<ZepDisplay_Qt>()),
          m_editor(m_display, "/path/to/root") {}
    
    void paintEvent(QPaintEvent* event) override {
        QPainter painter(this);
        
        // Set the painter for Zep to use
        std::static_pointer_cast<ZepDisplay_Qt>(m_display)->SetPainter(&painter);
        
        // Update editor size and draw
        m_editor.SetDisplayRegion(NVec2f(width(), height()));
        m_editor.Display();
    }
    
private:
    std::shared_ptr<ZepDisplay_Qt> m_display;
    ZepEditor m_editor;
};

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Platform Differences

  • macOS: Uses Menlo font by default
  • Other platforms: Uses Consolas font by default
  • Both fall back to Qt’s generic monospace font if the preferred font is unavailable

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