Revert back to using QGraphicsView but with a custom QGraphicsItem.

This change keeps the previous performance improvements from commit 8de96dc... but changes back to using QGraphicsView with the custom QWidget modified to a custom QGraphicsItem. The reason for this change is for much better dragging and scrolling support. QGraphicsView supports dragging natively, and supports the centerOn() function, which are not naturally supported in QScrollArea.
damaki · Feb 8, 2016 · 8be239a · 8be239a
1 parent 0c4eeea
commit 8be239a
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Showing 9 changed files with 277 additions and 135 deletions.
diff --git a/forms/mainwindow.ui b/forms/mainwindow.ui
@@ -23,47 +23,19 @@
       <property name="orientation">
        <enum>Qt::Vertical</enum>
       </property>
-      <property name="opaqueResize">
-       <bool>true</bool>
-      </property>
-      <widget class="QScrollArea" name="scrollArea">
+      <widget class="QGraphicsView" name="graphicsView">
        <property name="sizePolicy">
-        <sizepolicy hsizetype="Expanding" vsizetype="MinimumExpanding">
+        <sizepolicy hsizetype="Expanding" vsizetype="Preferred">
          <horstretch>0</horstretch>
          <verstretch>0</verstretch>
         </sizepolicy>
        </property>
-       <property name="minimumSize">
-        <size>
-         <width>782</width>
-         <height>78</height>
-        </size>
-       </property>
-       <property name="baseSize">
-        <size>
-         <width>0</width>
-         <height>0</height>
-        </size>
-       </property>
-       <property name="sizeAdjustPolicy">
-        <enum>QAbstractScrollArea::AdjustToContentsOnFirstShow</enum>
-       </property>
-       <property name="widgetResizable">
-        <bool>true</bool>
+       <property name="dragMode">
+        <enum>QGraphicsView::ScrollHandDrag</enum>
        </property>
-       <property name="alignment">
-        <set>Qt::AlignCenter</set>
+       <property name="resizeAnchor">
+        <enum>QGraphicsView::AnchorViewCenter</enum>
        </property>
-       <widget class="QWidget" name="scrollAreaWidgetContents">
-        <property name="geometry">
-         <rect>
-          <x>0</x>
-          <y>0</y>
-          <width>780</width>
-          <height>76</height>
-         </rect>
-        </property>
-       </widget>
       </widget>
       <widget class="QWidget" name="">
        <layout class="QHBoxLayout" name="horizontalLayout">

diff --git a/src/commandrunner.cpp b/src/commandrunner.cpp
@@ -22,7 +22,7 @@
 #include <QMutexLocker>
 #include <cassert>
 
-CommandRunner::CommandRunner(TurtleGraphicsWidget* const graphicsWidget) :
+CommandRunner::CommandRunner(TurtleGraphicsItem* const graphicsWidget) :
     m_state(luaL_newstate()),
     m_graphicsWidget(graphicsWidget),
     m_scriptDataSema(),
@@ -52,7 +52,7 @@ CommandRunner::CommandRunner(TurtleGraphicsWidget* const graphicsWidget) :
     setupCommands(m_state, this);
 }
 
-TurtleGraphicsWidget* CommandRunner::graphicsWidget() const
+TurtleGraphicsItem* CommandRunner::graphicsWidget() const
 {
     return m_graphicsWidget;
 }

diff --git a/src/commandrunner.h b/src/commandrunner.h
@@ -38,9 +38,9 @@ class CommandRunner : public QThread
     Q_OBJECT
 
 public:
-    CommandRunner(TurtleGraphicsWidget* graphicsWidget);
+    CommandRunner(TurtleGraphicsItem* graphicsWidget);
 
-    TurtleGraphicsWidget* graphicsWidget() const;
+    TurtleGraphicsItem* graphicsWidget() const;
 
     void requestThreadStop();
 
@@ -64,7 +64,7 @@ class CommandRunner : public QThread
 
 private:
     lua_State* m_state;
-    TurtleGraphicsWidget* m_graphicsWidget;
+    TurtleGraphicsItem* m_graphicsWidget;
 
     mutable QMutex m_luaMutex; // locked while a script is running
 

diff --git a/src/mainwindow.cpp b/src/mainwindow.cpp
@@ -24,30 +24,28 @@
 #include <cmath>
 #include <iostream>
 
-static const int VIEW_UPDATE_DELAY = 33; // update every 33ms (~30 fps)
-
 MainWindow::MainWindow(QWidget *parent) :
     QMainWindow(parent),
     ui(new Ui::MainWindow),
-    m_turtleGraphics(new TurtleGraphicsWidget),
+    m_scene(new QGraphicsScene),
+    m_turtleGraphics(new TurtleGraphicsItem),
     m_cmds(m_turtleGraphics),
     m_prefsDialog(new PreferencesDialog(m_turtleGraphics, this)),
     m_helpDialog(new HelpDialog(this))
 {
     ui->setupUi(this);
 
-    m_turtleGraphics->show();
-    ui->scrollArea->setWidget(m_turtleGraphics);
+    ui->graphicsView->setScene(m_scene);
+    m_scene->addItem(m_turtleGraphics);
 
-    // Make the scroll area occupy as much as possible.
-    // (the size will be constrained to the maximum possible according to the
-    //  layout, which will be less than this MainWindow's size).
-    ui->scrollArea->resize(width(), height());
+    ui->graphicsView->centerOn(0.0, 0.0);
 
     ui->haltButton->setEnabled(false);
     ui->pauseButton->setEnabled(false);
     ui->resumeButton->setEnabled(false);
 
+    connect(m_turtleGraphics, SIGNAL(canvasResized()), this, SLOT(resizeGraphicsScene()));
+
     connect(ui->runButton,    SIGNAL(clicked()), this, SLOT(runCommand()));
     connect(ui->haltButton,   SIGNAL(clicked()), this, SLOT(haltCommand()));
     connect(ui->pauseButton,  SIGNAL(clicked()), this, SLOT(pauseCommand()));
@@ -98,6 +96,11 @@ void MainWindow::handleError(const QString& message)
     std::cerr << message.toStdString() << std::endl;
 }
 
+/**
+ * @brief Called when a command finishes executing.
+ *
+ * This method updates the UI's buttons to allow another command to be executed.
+ */
 void MainWindow::commandFinished()
 {
     ui->runButton->setEnabled(true);
@@ -106,6 +109,9 @@ void MainWindow::commandFinished()
     ui->resumeButton->setEnabled(false);
 }
 
+/**
+ * @brief Pauses the currently executing command(s)
+ */
 void MainWindow::pauseCommand()
 {
     ui->pauseButton->setEnabled(false);
@@ -114,6 +120,9 @@ void MainWindow::pauseCommand()
     m_cmds.requestCommandPause();
 }
 
+/**
+ * @brief Resumes a previously paused command.
+ */
 void MainWindow::resumeCommand()
 {
     ui->pauseButton->setEnabled(true);
@@ -122,6 +131,9 @@ void MainWindow::resumeCommand()
     m_cmds.requestCommandResume();
 }
 
+/**
+ * @brief Halts/stops/aborts the currently running command.
+ */
 void MainWindow::haltCommand()
 {
     ui->runButton->setEnabled(false);
@@ -131,3 +143,13 @@ void MainWindow::haltCommand()
 
     m_cmds.requestCommandHalt();
 }
+
+/**
+ * @brief Resets the QGraphicsScene to perfectly fit the turtle graphic's bounding box.
+ *
+ * This avoids unused space around the drawing canvas when the canvas size is reduced.
+ */
+void MainWindow::resizeGraphicsScene()
+{
+    m_scene->setSceneRect(m_turtleGraphics->boundingRect().translated(m_turtleGraphics->pos()));
+}
diff --git a/src/mainwindow.h b/src/mainwindow.h
@@ -53,10 +53,13 @@ private slots:
     void resumeCommand();
     void haltCommand();
 
+    void resizeGraphicsScene();
+
 private:
     Ui::MainWindow *ui;
 
-    TurtleGraphicsWidget* m_turtleGraphics;
+    QGraphicsScene* m_scene;
+    TurtleGraphicsItem* m_turtleGraphics;
     CommandRunner m_cmds;
 
     PreferencesDialog* m_prefsDialog;

diff --git a/src/preferencesdialog.cpp b/src/preferencesdialog.cpp
@@ -20,7 +20,7 @@
 #include "preferencesdialog.h"
 #include "ui_preferencesdialog.h"
 
-PreferencesDialog::PreferencesDialog(TurtleGraphicsWidget* const graphicsWidget,
+PreferencesDialog::PreferencesDialog(TurtleGraphicsItem* const graphicsWidget,
                                      QWidget* const parent) :
     QDialog(parent),
     ui(new Ui::PreferencesDialog),
@@ -41,7 +41,7 @@ void PreferencesDialog::loadPreferences()
     if (NULL != m_graphicsWidget)
     {
         ui->antialiasingCheckBox->setChecked(m_graphicsWidget->antialiased());
-        ui->canvasSizeSpinBox->setValue(m_graphicsWidget->width());
+        ui->canvasSizeSpinBox->setValue(m_graphicsWidget->boundingRect().width());
     }
 }
 
@@ -52,6 +52,6 @@ void PreferencesDialog::applyPreferences()
         m_graphicsWidget->setAntialiased(ui->antialiasingCheckBox->checkState() == Qt::Checked);
 
         const int newSize = ui->canvasSizeSpinBox->value();
-        m_graphicsWidget->setFixedSize(newSize, newSize);
+        m_graphicsWidget->resize(newSize);
     }
 }
diff --git a/src/preferencesdialog.h b/src/preferencesdialog.h
@@ -35,7 +35,7 @@ class PreferencesDialog : public QDialog
     Q_OBJECT
 
 public:
-    PreferencesDialog(TurtleGraphicsWidget* graphicsWidget, QWidget* parent = 0);
+    PreferencesDialog(TurtleGraphicsItem* graphicsWidget, QWidget* parent = 0);
     ~PreferencesDialog();
 
 public slots:
@@ -45,7 +45,7 @@ public slots:
 private:
     Ui::PreferencesDialog* ui;
 
-    TurtleGraphicsWidget* m_graphicsWidget;
+    TurtleGraphicsItem* m_graphicsWidget;
 };
 
 #endif // PREFERENCESDIALOG_H