LogWidget: Replace QTextEdit with QPlainTextEdit for better performance

QTextEdit is heavy, similar in functionality to WordPad,
while QPlainTextEdit is lightweight like Notepad.
Qt documentation recommends using QPlainTextEdit for log viewers,
and it also allows to set automatic cutoff of oldest messages beyond a fixed point,
which we now set to MAX_LOG_LINES (5000)

2 files changed, 19 insertions, 17 deletions

diff --git a/Source/Core/DolphinQt/Config/LogWidget.cpp b/Source/Core/DolphinQt/Config/LogWidget.cpp
index 2b5f4dfdc4..e3567353b0 100644
--- a/Source/Core/DolphinQt/Config/LogWidget.cpp
+++ b/Source/Core/DolphinQt/Config/LogWidget.cpp
@@ -8,12 +8,13 @@
 #include <QComboBox>
 #include <QFont>
 #include <QFontDatabase>
-#include <QGroupBox>
+#include <QGridLayout>
+#include <QPlainTextEdit>
 #include <QPushButton>
 #include <QScrollBar>
-#include <QTextEdit>
 #include <QTimer>
-#include <QVBoxLayout>
+
+#include "Core/ConfigManager.h"
 
 #include "Common/FileUtil.h"
 #include "Common/StringUtil.h"
@@ -25,8 +26,10 @@
 
 // Delay in ms between calls of UpdateLog()
 constexpr int UPDATE_LOG_DELAY = 100;
+// Maximum number of lines to show in log viewer
+constexpr int MAX_LOG_LINES = 5000;
 // Maximum lines to process at a time
-constexpr int MAX_LOG_LINES = 200;
+constexpr size_t MAX_LOG_LINES_TO_UPDATE = 200;
 // Timestamp length
 constexpr int TIMESTAMP_LENGTH = 10;
 
@@ -75,9 +78,9 @@ void LogWidget::UpdateLog()
   int old_horizontal = hscroll->value();
   int old_vertical = vscroll->value();
 
-  for (int i = 0; !m_log_queue.empty() && i < MAX_LOG_LINES; i++)
+  for (size_t i = 0; !m_log_queue.empty() && i < MAX_LOG_LINES_TO_UPDATE; i++)
   {
-    m_log_text->append(m_log_queue.front());
+    m_log_text->appendHtml(m_log_queue.front());
     m_log_queue.pop();
   }
 
@@ -115,8 +118,7 @@ void LogWidget::UpdateFont()
 void LogWidget::CreateWidgets()
 {
   // Log
-  m_tab_log = new QWidget;
-  m_log_text = new QTextEdit;
+  m_log_text = new QPlainTextEdit;
   m_log_wrap = new QCheckBox(tr("Word Wrap"));
   m_log_font = new QComboBox;
   m_log_clear = new QPushButton(tr("Clear"));
@@ -124,7 +126,6 @@ void LogWidget::CreateWidgets()
   m_log_font->addItems({tr("Default Font"), tr("Monospaced Font"), tr("Selected Font")});
 
   auto* log_layout = new QGridLayout;
-  m_tab_log->setLayout(log_layout);
   log_layout->addWidget(m_log_wrap, 0, 0);
   log_layout->addWidget(m_log_font, 0, 1);
   log_layout->addWidget(m_log_clear, 0, 2);
@@ -136,6 +137,8 @@ void LogWidget::CreateWidgets()
   setWidget(widget);
 
   m_log_text->setReadOnly(true);
+  m_log_text->setUndoRedoEnabled(false);
+  m_log_text->setMaximumBlockCount(MAX_LOG_LINES);
 
   QPalette palette = m_log_text->palette();
   palette.setColor(QPalette::Base, Qt::black);
@@ -145,7 +148,7 @@ void LogWidget::CreateWidgets()
 
 void LogWidget::ConnectWidgets()
 {
-  connect(m_log_clear, &QPushButton::clicked, m_log_text, &QTextEdit::clear);
+  connect(m_log_clear, &QPushButton::clicked, m_log_text, &QPlainTextEdit::clear);
   connect(m_log_wrap, &QCheckBox::toggled, this, &LogWidget::SaveSettings);
   connect(m_log_font, static_cast<void (QComboBox::*)(int)>(&QComboBox::currentIndexChanged), this,
           &LogWidget::SaveSettings);
@@ -163,7 +166,8 @@ void LogWidget::LoadSettings()
 
   // Log - Wrap Lines
   m_log_wrap->setChecked(settings.value(QStringLiteral("logging/wraplines")).toBool());
-  m_log_text->setLineWrapMode(m_log_wrap->isChecked() ? QTextEdit::WidgetWidth : QTextEdit::NoWrap);
+  m_log_text->setLineWrapMode(m_log_wrap->isChecked() ? QPlainTextEdit::WidgetWidth :
+                                                        QPlainTextEdit::NoWrap);
 
   // Log - Font Selection
   // Currently "Debugger Font" is not supported as there is no Qt Debugger, defaulting to Monospace
@@ -180,7 +184,8 @@ void LogWidget::SaveSettings()
 
   // Log - Wrap Lines
   settings.setValue(QStringLiteral("logging/wraplines"), m_log_wrap->isChecked());
-  m_log_text->setLineWrapMode(m_log_wrap->isChecked() ? QTextEdit::WidgetWidth : QTextEdit::NoWrap);
+  m_log_text->setLineWrapMode(m_log_wrap->isChecked() ? QPlainTextEdit::WidgetWidth :
+                                                        QPlainTextEdit::NoWrap);
 
   // Log - Font Selection
   settings.setValue(QStringLiteral("logging/font"), m_log_font->currentIndex());
diff --git a/Source/Core/DolphinQt/Config/LogWidget.h b/Source/Core/DolphinQt/Config/LogWidget.h
index d116d8d02b..d8956cca1d 100644
--- a/Source/Core/DolphinQt/Config/LogWidget.h
+++ b/Source/Core/DolphinQt/Config/LogWidget.h
@@ -14,9 +14,8 @@
 class QCheckBox;
 class QCloseEvent;
 class QComboBox;
+class QPlainTextEdit;
 class QPushButton;
-class QVBoxLayout;
-class QTextEdit;
 class QTimer;
 
 class LogWidget final : public QDockWidget, LogListener
@@ -43,9 +42,7 @@ private:
   QCheckBox* m_log_wrap;
   QComboBox* m_log_font;
   QPushButton* m_log_clear;
-  QVBoxLayout* m_main_layout;
-  QTextEdit* m_log_text;
-  QWidget* m_tab_log;
+  QPlainTextEdit* m_log_text;
 
   QTimer* m_timer;