Fix Style Plugin Example, and add some CMake Docs

A few things:

- Improved the documentation by adding a CMake section, briefly
  describing the process of adding the plugin, and placing it where it
  should be.
- Write a note about the case where the style may be overwritten at
  launch, and how to set the a new style using a CLI
- Improved the CMake build such that it creates the App Bundle
  correctly, and also works without an App Bundle as well.
- Changed the example, and plugin such that now instead of a QPushButton
  we have a QTextEdit, and change the text color.
- Replaced the application screenshot

Fixes: QTBUG-107842
Fixes: QTBUG-109227
Change-Id: I161a91b27df016ff6230fac3871b79d2dfbdf18a
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>

5 files changed, 44 insertions, 11 deletions

diff --git a/examples/widgets/tools/styleplugin/plugin/CMakeLists.txt b/examples/widgets/tools/styleplugin/plugin/CMakeLists.txt
index 41df10c578..b82d3ab065 100644
--- a/examples/widgets/tools/styleplugin/plugin/CMakeLists.txt
+++ b/examples/widgets/tools/styleplugin/plugin/CMakeLists.txt
@@ -1,15 +1,33 @@
 # Copyright (C) 2022 The Qt Company Ltd.
 # SPDX-License-Identifier: BSD-3-Clause
 
+#! [0]
 qt_add_plugin(simplestyleplugin
     CLASS_NAME SimpleStylePlugin
     simplestyle.cpp simplestyle.h
     simplestyleplugin.cpp simplestyleplugin.h
 )
+#! [0]
 
-set_target_properties(simplestyleplugin PROPERTIES
-    LIBRARY_OUTPUT_DIRECTORY "${PROJECT_BINARY_DIR}/stylewindow/styles"
-)
+if(QT_FEATURE_debug AND APPLE)
+    set_property(simplestyleplugin
+       APPEND_STRING PROPERTY OUTPUT_NAME "_debug")
+endif()
+
+get_target_property(is_bundle styleplugin MACOSX_BUNDLE)
+if(APPLE AND is_bundle)
+#! [1]
+    set_target_properties(simplestyleplugin PROPERTIES
+        LIBRARY_OUTPUT_DIRECTORY "$<TARGET_BUNDLE_CONTENT_DIR:styleplugin>/PlugIns/styles"
+    )
+#! [1]
+else()
+#! [2]
+    set_target_properties(simplestyleplugin PROPERTIES
+        LIBRARY_OUTPUT_DIRECTORY "$<TARGET_FILE_DIR:styleplugin>/styles"
+    )
+#! [2]
+endif()
 
 target_link_libraries(simplestyleplugin PRIVATE
     Qt6::Core
diff --git a/examples/widgets/tools/styleplugin/plugin/plugin.pro b/examples/widgets/tools/styleplugin/plugin/plugin.pro
index 35184fc82a..5ab00016ca 100644
--- a/examples/widgets/tools/styleplugin/plugin/plugin.pro
+++ b/examples/widgets/tools/styleplugin/plugin/plugin.pro
@@ -12,7 +12,17 @@ win32 {
     CONFIG(debug, release|debug):DESTDIR = ../debug/styles/
     CONFIG(release, release|debug):DESTDIR = ../release/styles/
 } else {
-    DESTDIR = ../styles/
+    macos {
+        # The non-app-bundle case is not supported with qmake, because
+        # the plugin project cannot know whether the app is built
+        # as a bundle or not.
+        DESTDIR = ../styleplugin.app/Contents/PlugIns/styles/
+        contains(QT_CONFIG, debug) {
+            TARGET = $$join(TARGET,,,_debug)
+        }
+    } else {
+        DESTDIR = ../styles/
+    }
 }
 
 EXAMPLE_FILES += simplestyle.json
diff --git a/examples/widgets/tools/styleplugin/plugin/simplestyle.cpp b/examples/widgets/tools/styleplugin/plugin/simplestyle.cpp
index 93bea72bcd..fa60d50140 100644
--- a/examples/widgets/tools/styleplugin/plugin/simplestyle.cpp
+++ b/examples/widgets/tools/styleplugin/plugin/simplestyle.cpp
@@ -5,5 +5,5 @@
 
 void SimpleStyle::polish(QPalette &palette)
 {
-    palette.setBrush(QPalette::Button, Qt::red);
+    palette.setBrush(QPalette::Text, Qt::red);
 }
diff --git a/examples/widgets/tools/styleplugin/stylewindow/main.cpp b/examples/widgets/tools/styleplugin/stylewindow/main.cpp
index 0b4ca6320f..0b0a295410 100644
--- a/examples/widgets/tools/styleplugin/stylewindow/main.cpp
+++ b/examples/widgets/tools/styleplugin/stylewindow/main.cpp
@@ -10,10 +10,15 @@
 int main(int argv, char *args[])
 {
     QApplication app(argv, args);
-    QApplication::setStyle(QStyleFactory::create("simplestyle"));
+
+    QStyle *style = QStyleFactory::create("simplestyle");
+    if (!style)
+        qFatal("Cannot load the 'simplestyle' plugin.");
+
+    QApplication::setStyle(style);
 
     StyleWindow window;
-    window.resize(200, 50);
+    window.resize(350, 50);
     window.show();
 
     return app.exec();
diff --git a/examples/widgets/tools/styleplugin/stylewindow/stylewindow.cpp b/examples/widgets/tools/styleplugin/stylewindow/stylewindow.cpp
index fd449057e6..9268666c21 100644
--- a/examples/widgets/tools/styleplugin/stylewindow/stylewindow.cpp
+++ b/examples/widgets/tools/styleplugin/stylewindow/stylewindow.cpp
@@ -3,18 +3,18 @@
 
 #include <QGridLayout>
 #include <QGroupBox>
-#include <QPushButton>
+#include <QTextEdit>
 
 #include "stylewindow.h"
 
 StyleWindow::StyleWindow()
 {
-    QPushButton *styledButton = new QPushButton(tr("Big Red Button"));
+    QTextEdit *styledTextEdit = new QTextEdit(tr("The quick brown fox jumps over the lazy dog"));
 
     QGridLayout *layout = new QGridLayout;
-    layout->addWidget(styledButton);
+    layout->addWidget(styledTextEdit);
 
-    QGroupBox *styleBox = new QGroupBox(tr("A simple style button"));
+    QGroupBox *styleBox = new QGroupBox(tr("A simple styled text edit"));
     styleBox->setLayout(layout);
 
     QGridLayout *outerLayout = new QGridLayout;