PaintBrush: Add a "line" tool for drawing straight lines

This implements "preview" of the line by allowing tool subclasses to
hook the second_paint_event on the PaintableWidget.

Work towards #375.

Applications/PaintBrush/LineTool.cpp

@@ -0,0 +1,79 @@
+#include "LineTool.h"
+#include "PaintableWidget.h"
+#include <LibGUI/GAction.h>
+#include <LibGUI/GMenu.h>
+#include <LibGUI/GPainter.h>
+
+LineTool::LineTool()
+{
+}
+
+LineTool::~LineTool()
+{
+}
+
+void LineTool::on_mousedown(GMouseEvent& event)
+{
+    if (event.button() != GMouseButton::Left && event.button() != GMouseButton::Right)
+        return;
+
+    if (m_drawing_button != GMouseButton::None)
+        return;
+
+    m_drawing_button = event.button();
+    m_line_start_position = event.position();
+    m_line_end_position = event.position();
+    m_widget->update();
+}
+
+void LineTool::on_mouseup(GMouseEvent& event)
+{
+    if (event.button() == m_drawing_button) {
+        GPainter painter(m_widget->bitmap());
+        painter.draw_line(m_line_start_position, m_line_end_position, m_widget->color_for(m_drawing_button), m_thickness);
+        m_drawing_button = GMouseButton::None;
+        m_widget->update();
+    }
+}
+
+void LineTool::on_mousemove(GMouseEvent& event)
+{
+    if (m_drawing_button == GMouseButton::None)
+        return;
+
+    if (!m_widget->rect().contains(event.position()))
+        return;
+
+    m_line_end_position = event.position();
+    m_widget->update();
+}
+
+void LineTool::on_second_paint(GPaintEvent& event)
+{
+    if (m_drawing_button == GMouseButton::None)
+        return;
+
+    GPainter painter(*m_widget);
+    painter.add_clip_rect(event.rect());
+    painter.draw_line(m_line_start_position, m_line_end_position, m_widget->color_for(m_drawing_button), m_thickness);
+}
+
+void LineTool::on_contextmenu(GContextMenuEvent& event)
+{
+    if (!m_context_menu) {
+        m_context_menu = make<GMenu>();
+        m_context_menu->add_action(GAction::create("1", [this](auto&) {
+            m_thickness = 1;
+        }));
+        m_context_menu->add_action(GAction::create("2", [this](auto&) {
+            m_thickness = 2;
+        }));
+        m_context_menu->add_action(GAction::create("3", [this](auto&) {
+            m_thickness = 3;
+        }));
+        m_context_menu->add_action(GAction::create("4", [this](auto&) {
+            m_thickness = 4;
+        }));
+    }
+    m_context_menu->popup(event.screen_position());
+}

Applications/PaintBrush/LineTool.h

@@ -0,0 +1,27 @@
+#pragma once
+
+#include "Tool.h"
+#include <LibDraw/Point.h>
+
+class GMenu;
+
+class LineTool final : public Tool {
+public:
+    LineTool();
+    virtual ~LineTool() override;
+
+    virtual void on_mousedown(GMouseEvent&) override;
+    virtual void on_mousemove(GMouseEvent&) override;
+    virtual void on_mouseup(GMouseEvent&) override;
+    virtual void on_contextmenu(GContextMenuEvent&) override;
+    virtual void on_second_paint(GPaintEvent&) override;
+
+private:
+    virtual const char* class_name() const override { return "LineTool"; }
+
+    GMouseButton m_drawing_button { GMouseButton::None };
+    Point m_line_start_position;
+    Point m_line_end_position;
+    OwnPtr<GMenu> m_context_menu;
+    int m_thickness { 1 };
+};

Applications/PaintBrush/Makefile

@@ -6,6 +6,7 @@ OBJS = \
     ToolboxWidget.o \
     Tool.o \
     PenTool.o \
+    LineTool.o \
     EraseTool.o \
     BucketTool.o \
     ColorDialog.o \

Applications/PaintBrush/PaintableWidget.cpp

@@ -46,7 +46,16 @@ Tool* PaintableWidget::tool()
     return m_tool;
 }
 
-Color PaintableWidget::color_for(const GMouseEvent& event)
+Color PaintableWidget::color_for(GMouseButton button) const
+{
+    if (button == GMouseButton::Left)
+        return m_primary_color;
+    if (button == GMouseButton::Right)
+        return m_secondary_color;
+    ASSERT_NOT_REACHED();
+}
+
+Color PaintableWidget::color_for(const GMouseEvent& event) const
 {
     if (event.buttons() & GMouseButton::Left)
         return m_primary_color;
@@ -80,6 +89,13 @@ void PaintableWidget::mousemove_event(GMouseEvent& event)
     GWidget::mousemove_event(event);
 }
 
+void PaintableWidget::second_paint_event(GPaintEvent& event)
+{
+    if (m_tool)
+        m_tool->on_second_paint(event);
+    GWidget::second_paint_event(event);
+}
+
 void PaintableWidget::set_primary_color(Color color)
 {
     if (m_primary_color == color)

Applications/PaintBrush/PaintableWidget.h

@@ -20,7 +20,8 @@ public:
     void set_tool(Tool* tool);
     Tool* tool();
 
-    Color color_for(const GMouseEvent&);
+    Color color_for(const GMouseEvent&) const;
+    Color color_for(GMouseButton) const;
 
     void set_bitmap(const GraphicsBitmap&);
 
@@ -32,6 +33,7 @@ public:
 
 private:
     virtual void paint_event(GPaintEvent&) override;
+    virtual void second_paint_event(GPaintEvent&) override;
     virtual void mousedown_event(GMouseEvent&) override;
     virtual void mouseup_event(GMouseEvent&) override;
     virtual void mousemove_event(GMouseEvent&) override;

Applications/PaintBrush/Tool.h

@@ -9,10 +9,11 @@ public:
 
     virtual const char* class_name() const = 0;
 
-    virtual void on_mousedown(GMouseEvent&) { }
-    virtual void on_mousemove(GMouseEvent&) { }
-    virtual void on_mouseup(GMouseEvent&) { }
-    virtual void on_contextmenu(GContextMenuEvent&) { }
+    virtual void on_mousedown(GMouseEvent&) {}
+    virtual void on_mousemove(GMouseEvent&) {}
+    virtual void on_mouseup(GMouseEvent&) {}
+    virtual void on_contextmenu(GContextMenuEvent&) {}
+    virtual void on_second_paint(GPaintEvent&) {}
 
     void clear() { m_widget = nullptr; }
     void setup(PaintableWidget& widget) { m_widget = widget.make_weak_ptr(); }

Applications/PaintBrush/ToolboxWidget.cpp

@@ -1,13 +1,14 @@
 #include "ToolboxWidget.h"
 #include "BucketTool.h"
-#include "SprayTool.h"
+#include "EraseTool.h"
+#include "LineTool.h"
 #include "PaintableWidget.h"
 #include "PenTool.h"
 #include "PickerTool.h"
-#include "EraseTool.h"
+#include "SprayTool.h"
+#include <LibDraw/PNGLoader.h>
 #include <LibGUI/GBoxLayout.h>
 #include <LibGUI/GButton.h>
-#include <LibDraw/PNGLoader.h>
 
 class ToolButton final : public GButton {
     C_OBJECT(ToolButton)
@@ -69,6 +70,7 @@ ToolboxWidget::ToolboxWidget(GWidget* parent)
     add_tool("Spray", "spray", make<SprayTool>());
     add_tool("Color Picker", "picker", make<PickerTool>());
     add_tool("Erase", "eraser", make<EraseTool>());
+    add_tool("Line", "line", make<LineTool>());
 }
 
 ToolboxWidget::~ToolboxWidget()