Start working on a simple graphical font editor.

Editing fonts by editing text files is really slow and boring.
A simple font editor seems like a good way to take LibGUI for a spin.

FontEditor/FontEditor.cpp

@@ -0,0 +1,192 @@
+#include "FontEditor.h"
+#include <SharedGraphics/Painter.h>
+#include <LibGUI/GLabel.h>
+
+FontEditorWidget::FontEditorWidget(GWidget* parent)
+    : GWidget(parent)
+{
+    auto mutable_font = Font::default_font().clone();
+
+    m_glyph_map_widget = new GlyphMapWidget(*mutable_font, this);
+    m_glyph_map_widget->move_to({ 90, 5 });
+
+    m_glyph_editor_widget = new GlyphEditorWidget(*mutable_font, this);
+    m_glyph_editor_widget->move_to({ 5, 5 });
+
+    auto* label = new GLabel(this);
+    label->set_relative_rect({ 5, 110, 140, 20 });
+
+    m_glyph_editor_widget->on_glyph_altered = [this] {
+        m_glyph_map_widget->update();
+    };
+
+    m_glyph_map_widget->on_glyph_selected = [this, label] (byte glyph) {
+        m_glyph_editor_widget->set_glyph(glyph);
+        label->set_text(String::format("Glyph: 0x%b (%c)", glyph, glyph));
+    };
+
+    m_glyph_map_widget->set_selected_glyph('A');
+}
+
+FontEditorWidget::~FontEditorWidget()
+{
+}
+
+GlyphMapWidget::GlyphMapWidget(Font& mutable_font, GWidget* parent)
+    : GWidget(parent)
+    , m_font(mutable_font)
+{
+    set_relative_rect({ 0, 0, preferred_width(), preferred_height() });
+}
+
+GlyphMapWidget::~GlyphMapWidget()
+{
+}
+
+int GlyphMapWidget::preferred_width() const
+{
+    return columns() * (font().glyph_width() + m_horizontal_spacing);
+}
+
+int GlyphMapWidget::preferred_height() const
+{
+    return rows() * (font().glyph_height() + m_vertical_spacing);
+}
+
+void GlyphMapWidget::set_selected_glyph(byte glyph)
+{
+    if (m_selected_glyph == glyph)
+        return;
+    m_selected_glyph = glyph;
+    if (on_glyph_selected)
+        on_glyph_selected(glyph);
+    update();
+}
+
+Rect GlyphMapWidget::get_outer_rect(byte glyph) const
+{
+    int row = glyph / columns();
+    int column = glyph % columns();
+    return {
+        column * (font().glyph_width() + m_horizontal_spacing),
+        row * (font().glyph_height() + m_vertical_spacing),
+        font().glyph_width() + m_horizontal_spacing,
+        font().glyph_height() + m_horizontal_spacing
+    };
+}
+
+void GlyphMapWidget::paint_event(GPaintEvent&)
+{
+    Painter painter(*this);
+    painter.set_font(font());
+    painter.fill_rect(rect(), Color::White);
+
+    byte glyph = 0;
+
+    for (int row = 0; row < rows(); ++row) {
+        for (int column = 0; column < columns(); ++column, ++glyph) {
+            Rect outer_rect = get_outer_rect(glyph);
+            Rect inner_rect(
+                outer_rect.x() + m_horizontal_spacing / 2,
+                outer_rect.y() + m_vertical_spacing / 2,
+                font().glyph_width(),
+                font().glyph_height()
+            );
+            if (glyph == m_selected_glyph) {
+                painter.fill_rect(outer_rect, Color::Red);
+                painter.draw_glyph(inner_rect.location(), glyph, Color::White);
+            } else {
+                painter.draw_glyph(inner_rect.location(), glyph, Color::Black);
+            }
+        }
+    }
+}
+
+void GlyphMapWidget::mousedown_event(GMouseEvent& event)
+{
+    // FIXME: This is a silly loop.
+    for (unsigned glyph = 0; glyph < 256; ++glyph) {
+        if (get_outer_rect(glyph).contains(event.position())) {
+            set_selected_glyph(glyph);
+            break;
+        }
+    }
+}
+
+GlyphEditorWidget::GlyphEditorWidget(Font& mutable_font, GWidget* parent)
+    : GWidget(parent)
+    , m_font(mutable_font)
+{
+    set_relative_rect({ 0, 0, preferred_width(), preferred_height() });
+}
+
+GlyphEditorWidget::~GlyphEditorWidget()
+{
+}
+
+void GlyphEditorWidget::set_glyph(byte glyph)
+{
+    if (m_glyph == glyph)
+        return;
+    m_glyph = glyph;
+    update();
+}
+
+void GlyphEditorWidget::paint_event(GPaintEvent&)
+{
+    Painter painter(*this);
+    painter.fill_rect(rect(), Color::White);
+    painter.draw_rect(rect(), Color::Black);
+
+    auto& bitmap = font().glyph_bitmap(m_glyph);
+
+    for (int y = 0; y < font().glyph_height(); ++y) {
+        for (int x = 0; x < font().glyph_width(); ++x) {
+            Rect rect { x * m_scale, y * m_scale, m_scale, m_scale };
+            painter.fill_rect(rect, bitmap.bit_at(x, y) ? Color::Black : Color::White);
+        }
+    }
+}
+
+void GlyphEditorWidget::mousedown_event(GMouseEvent& event)
+{
+    draw_at_mouse(event);
+}
+
+void GlyphEditorWidget::mousemove_event(GMouseEvent& event)
+{
+    if (event.buttons() & (GMouseButton::Left | GMouseButton::Right))
+        draw_at_mouse(event);
+}
+
+void GlyphEditorWidget::draw_at_mouse(const GMouseEvent& event)
+{
+    bool set = event.buttons() & GMouseButton::Left;
+    bool unset = event.buttons() & GMouseButton::Right;
+    if (!(set ^ unset))
+        return;
+    byte new_bit = set ? '#' : ' ';
+    int x = event.x() / m_scale;
+    int y = event.y() / m_scale;
+    auto& bitmap = font().glyph_bitmap(m_glyph);
+    auto* mutable_bits = const_cast<char*>(bitmap.bits());
+    ASSERT((unsigned)x < bitmap.width());
+    ASSERT((unsigned)y < bitmap.height());
+    auto& bit = mutable_bits[y * bitmap.width() + x];
+    if (bit == new_bit)
+        return;
+    bit = new_bit;
+    if (on_glyph_altered)
+        on_glyph_altered();
+    update();
+}
+
+int GlyphEditorWidget::preferred_width() const
+{
+    return font().glyph_width() * m_scale;
+}
+
+int GlyphEditorWidget::preferred_height() const
+{
+    return font().glyph_height() * m_scale;
+}