PixelPaint: Draw the current editor selection as marching ants

This patch moves the marching ants painting code to Selection and
unifies the timer mechanism so that all marching ants are synchronized
which looks neat. :^)

1 files changed, 42 insertions, 1 deletions

diff --git a/Userland/Applications/PixelPaint/Selection.cpp b/Userland/Applications/PixelPaint/Selection.cpp
index db93e751f0..6e645e9ddb 100644
--- a/Userland/Applications/PixelPaint/Selection.cpp
+++ b/Userland/Applications/PixelPaint/Selection.cpp
@@ -10,9 +10,50 @@
 
 namespace PixelPaint {
 
+constexpr int marching_ant_length = 4;
+
 void Selection::paint(Gfx::Painter& painter, ImageEditor const& editor)
 {
-    painter.draw_rect(editor.image_rect_to_editor_rect(m_rect).to_type<int>(), Color::Magenta);
+    draw_marching_ants(painter, editor.image_rect_to_editor_rect(m_rect).to_type<int>());
+}
+
+Selection::Selection(ImageEditor& editor)
+    : m_editor(editor)
+{
+    m_marching_ants_timer = Core::Timer::create_repeating(80, [this] {
+        ++m_marching_ants_offset;
+        m_marching_ants_offset %= marching_ant_length;
+        if (!is_empty())
+            m_editor.update();
+    });
+    m_marching_ants_timer->start();
+}
+
+void Selection::draw_marching_ants(Gfx::Painter& painter, Gfx::IntRect const& rect) const
+{
+    int offset = m_marching_ants_offset;
+
+    auto draw_pixel = [&](int x, int y) {
+        if ((offset % marching_ant_length) != 0)
+            painter.set_pixel(x, y, Color::Black);
+        offset++;
+    };
+
+    // Top line
+    for (int x = rect.left(); x <= rect.right(); ++x)
+        draw_pixel(x, rect.top());
+
+    // Right line
+    for (int y = rect.top() + 1; y <= rect.bottom(); ++y)
+        draw_pixel(rect.right(), y);
+
+    // Bottom line
+    for (int x = rect.right() - 1; x >= rect.left(); --x)
+        draw_pixel(x, rect.bottom());
+
+    // Left line
+    for (int y = rect.bottom() - 1; y > rect.top(); --y)
+        draw_pixel(rect.left(), y);
 }
 
 }