feat: add markdown file preview plugin

src/apps/dde-file-manager-preview/libdfm-preview/pluginInterface/filepreviewfactory.cpp

@@ -68,7 +68,7 @@
         qCWarning(logLibFilePreview) << "FilePreviewFactory: null preview instance provided for key compatibility check:" << key;
         return false;
     }
-    
+
     int index = FilePreviewFactory::previewToLoaderIndex.value(view, -1);
 
     if (index == -1) {
@@ -80,3 +80,15 @@
     qCDebug(logLibFilePreview) << "FilePreviewFactory: preview compatibility check for key:" << key << "result:" << suited;
     return suited;
 }
+
+bool FilePreviewFactory::hasPluginForKey(const QString &key)
+{
+#ifndef QT_NO_LIBRARY
+    int index = loader()->indexOf(key);
+    bool exists = (index != -1);
+    qCDebug(logLibFilePreview) << "FilePreviewFactory: plugin existence check for key:" << key << "result:" << exists;
+    return exists;
+#else
+    return false;
+#endif
+}

src/apps/dde-file-manager-preview/libdfm-preview/pluginInterface/filepreviewfactory.h

@@ -17,6 +17,7 @@ class FilePreviewFactory
     static QStringList keys();
     static DFMBASE_NAMESPACE::AbstractBasePreview *create(const QString &key);
     static bool isSuitedWithKey(const DFMBASE_NAMESPACE::AbstractBasePreview *view, const QString &key);
+    static bool hasPluginForKey(const QString &key);
 
     static QMap<const DFMBASE_NAMESPACE::AbstractBasePreview *, int> previewToLoaderIndex;
 };

src/apps/dde-file-manager-preview/libdfm-preview/views/filepreviewdialog.cpp

@@ -344,7 +344,22 @@ void FilePreviewDialog::switchToPage(int index)
     for (const QString &key : keyList) {
         const QString &gKey = generalKey(key);
 
-        if (preview && (FilePreviewFactory::isSuitedWithKey(preview, key) || FilePreviewFactory::isSuitedWithKey(preview, gKey)) && !FileUtils::isDesktopFile(fileList.at(index))) {
+        // Check if we can reuse existing preview, prioritize exact key match over general key
+        bool canReusePreview = false;
+        if (preview && !FileUtils::isDesktopFile(fileList.at(index))) {
+            // First check exact key match
+            if (FilePreviewFactory::isSuitedWithKey(preview, key)) {
+                canReusePreview = true;
+            } else if (gKey != key) {
+                // Only use general key if no exact key plugin exists
+                // This prevents text/* from intercepting text/markdown when markdown-preview exists
+                if (!FilePreviewFactory::hasPluginForKey(key)) {
+                    canReusePreview = FilePreviewFactory::isSuitedWithKey(preview, gKey);
+                }
+            }
+        }
+
+        if (canReusePreview) {
             qCDebug(logLibFilePreview) << "FilePreviewDialog: reusing existing preview for key:" << key;
             if (preview->setFileUrl(fileList.at(index))) {
                 preview->contentWidget()->updateGeometry();

src/apps/dde-file-manager-preview/pluginpreviews/CMakeLists.txt

@@ -6,6 +6,7 @@ include_directories(${CMAKE_CURRENT_SOURCE_DIR})
 add_subdirectory(image-preview)
 add_subdirectory(music-preview)
 add_subdirectory(text-preview)
+add_subdirectory(markdown-preview)
 add_subdirectory(dciicon-preview)
 add_subdirectory(pdf-preview)
 

src/apps/dde-file-manager-preview/pluginpreviews/markdown-preview/CMakeLists.txt

@@ -0,0 +1,39 @@
+cmake_minimum_required(VERSION 3.10)
+project(dde-markdown-preview-plugin)
+
+set(CMAKE_INCLUDE_CURRENT_DIR ON)
+
+FILE(GLOB_RECURSE MARKDOWNPREVIEW_FILES CONFIGURE_DEPENDS
+    "${CMAKE_CURRENT_SOURCE_DIR}/*.h"
+    "${CMAKE_CURRENT_SOURCE_DIR}/*.cpp"
+    "${CMAKE_CURRENT_SOURCE_DIR}/*.json"
+    "${GlobalFiles}"
+    )
+
+set(BIN_NAME ${PROJECT_NAME})
+
+find_package(Qt6 COMPONENTS Core REQUIRED)
+
+add_library(${BIN_NAME}
+    SHARED
+    ${MARKDOWNPREVIEW_FILES}
+)
+
+set_target_properties(${BIN_NAME} PROPERTIES LIBRARY_OUTPUT_DIRECTORY ${DFM_BUILD_PLUGIN_PREVIEW_DIR}/previews)
+
+target_link_libraries(${BIN_NAME}
+    DFM6::base
+    DFM6::framework
+)
+
+#install library file
+install(TARGETS
+    ${BIN_NAME}
+    LIBRARY
+    DESTINATION
+    ${DFM_PLUGIN_PREVIEW_DIR}
+)
+
+file(COPY ${CMAKE_CURRENT_SOURCE_DIR}/dde-markdown-preview-plugin.json DESTINATION ${DFM_BUILD_PLUGIN_PREVIEW_DIR}/previews)
+
+install(FILES ${CMAKE_CURRENT_SOURCE_DIR}/dde-markdown-preview-plugin.json DESTINATION ${DFM_PLUGIN_PREVIEW_DIR})

src/apps/dde-file-manager-preview/pluginpreviews/markdown-preview/dde-markdown-preview-plugin.json

@@ -0,0 +1,3 @@
+{
+    "Keys" : ["text/markdown"]
+}

src/apps/dde-file-manager-preview/pluginpreviews/markdown-preview/markdownbrowser.cpp

@@ -0,0 +1,51 @@
+// SPDX-FileCopyrightText: 2025 UnionTech Software Technology Co., Ltd.
+//
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#include "markdownbrowser.h"
+
+#include <QTextDocument>
+#include <QDebug>
+#include <QDir>
+
+using namespace plugin_filepreview;
+
+MarkdownBrowser::MarkdownBrowser(QWidget *parent)
+    : QTextBrowser(parent)
+{
+    setReadOnly(true);
+    setTextInteractionFlags(Qt::TextSelectableByMouse | Qt::TextSelectableByKeyboard | Qt::LinksAccessibleByMouse);
+    setOpenExternalLinks(true);
+    setLineWrapMode(QTextBrowser::WidgetWidth);
+    setFixedSize(800, 500);
+    setFrameStyle(QFrame::NoFrame);
+}
+
+MarkdownBrowser::~MarkdownBrowser()
+{
+}
+
+void MarkdownBrowser::setMarkdownContent(const QString &markdown, const QString &basePath)
+{
+    fmDebug() << "Markdown preview: setting markdown content, base path:" << basePath;
+
+    // Set base path for resolving relative image paths
+    if (!basePath.isEmpty()) {
+        QDir baseDir(basePath);
+        if (baseDir.exists()) {
+            document()->setMetaInformation(QTextDocument::DocumentUrl, QUrl::fromLocalFile(basePath).toString());
+            setSearchPaths(QStringList() << basePath);
+            fmDebug() << "Markdown preview: search paths set to:" << basePath;
+        } else {
+            fmWarning() << "Markdown preview: base path does not exist:" << basePath;
+        }
+    }
+
+    // Set markdown content using QTextDocument
+    document()->setMarkdown(markdown);
+
+    // Move cursor to the start of the document to ensure top of content is visible
+    moveCursor(QTextCursor::Start, QTextCursor::MoveAnchor);
+
+    fmInfo() << "Markdown preview: content set successfully";
+}

src/apps/dde-file-manager-preview/pluginpreviews/markdown-preview/markdownbrowser.h

@@ -0,0 +1,23 @@
+// SPDX-FileCopyrightText: 2025 UnionTech Software Technology Co., Ltd.
+//
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#ifndef MARKDOWNBROWSER_H
+#define MARKDOWNBROWSER_H
+#include "preview_plugin_global.h"
+
+#include <QTextBrowser>
+
+namespace plugin_filepreview {
+class MarkdownBrowser : public QTextBrowser
+{
+    Q_OBJECT
+public:
+    explicit MarkdownBrowser(QWidget *parent = nullptr);
+
+    virtual ~MarkdownBrowser() override;
+
+    void setMarkdownContent(const QString &markdown, const QString &basePath);
+};
+}
+#endif   // MARKDOWNBROWSER_H

src/apps/dde-file-manager-preview/pluginpreviews/markdown-preview/markdowncontextwidget.cpp

@@ -0,0 +1,35 @@
+// SPDX-FileCopyrightText: 2025 UnionTech Software Technology Co., Ltd.
+//
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#include "markdowncontextwidget.h"
+#include "markdownbrowser.h"
+
+#include <DPlainTextEdit>
+
+#include <QVBoxLayout>
+
+using namespace plugin_filepreview;
+DWIDGET_USE_NAMESPACE
+
+MarkdownContextWidget::MarkdownContextWidget(QWidget *parent)
+    : QWidget(parent)
+    , m_browserWidget(new MarkdownBrowser(this))
+{
+    DPlainTextEdit *titleWidget = new DPlainTextEdit(this);
+    titleWidget->setFixedHeight(30);
+    titleWidget->setFrameStyle(QFrame::NoFrame);
+    titleWidget->setReadOnly(true);
+    titleWidget->setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
+
+    QVBoxLayout *mainLay = new QVBoxLayout(this);
+    mainLay->addWidget(titleWidget);
+    mainLay->addWidget(m_browserWidget);
+    mainLay->setContentsMargins(0, 0, 0, 0);
+    mainLay->setSpacing(0);
+}
+
+MarkdownBrowser *MarkdownContextWidget::markdownBrowser() const
+{
+    return m_browserWidget;
+}

src/apps/dde-file-manager-preview/pluginpreviews/markdown-preview/markdowncontextwidget.h

@@ -0,0 +1,23 @@
+// SPDX-FileCopyrightText: 2025 UnionTech Software Technology Co., Ltd.
+//
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#ifndef MARKDOWNCONTEXTWIDGET_H
+#define MARKDOWNCONTEXTWIDGET_H
+
+#include <QWidget>
+
+namespace plugin_filepreview {
+class MarkdownBrowser;
+class MarkdownContextWidget : public QWidget
+{
+    Q_OBJECT
+public:
+    explicit MarkdownContextWidget(QWidget *parent = nullptr);
+    plugin_filepreview::MarkdownBrowser *markdownBrowser() const;
+
+private:
+    plugin_filepreview::MarkdownBrowser *m_browserWidget { nullptr };
+};
+}
+#endif // MARKDOWNCONTEXTWIDGET_H

src/apps/dde-file-manager-preview/pluginpreviews/markdown-preview/markdownpreview.cpp

@@ -0,0 +1,130 @@
+// SPDX-FileCopyrightText: 2025 UnionTech Software Technology Co., Ltd.
+//
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#include "markdownpreview.h"
+#include "markdownbrowser.h"
+#include "markdowncontextwidget.h"
+
+#include <dfm-base/interfaces/fileinfo.h>
+
+#include <QFile>
+#include <QFileInfo>
+#include <QTextStream>
+#include <QDebug>
+
+using namespace plugin_filepreview;
+DFMBASE_USE_NAMESPACE
+
+// 5MB maximum file size
+static constexpr qint64 kMaxReadSize { 1024 * 1024 * 5 };
+
+MarkdownPreview::MarkdownPreview(QObject *parent)
+    : AbstractBasePreview(parent)
+{
+    fmInfo() << "Markdown preview: MarkdownPreview instance created";
+}
+
+MarkdownPreview::~MarkdownPreview()
+{
+    fmInfo() << "Markdown preview: MarkdownPreview instance destroyed";
+    if (m_markdownBrowser) {
+        // Set parent to nullptr first to prevent recursive destruction issues
+        m_markdownBrowser->setParent(nullptr);
+        m_markdownBrowser->deleteLater();
+        m_markdownBrowser = nullptr;
+    }
+}
+
+bool MarkdownPreview::setFileUrl(const QUrl &url)
+{
+    fmInfo() << "Markdown preview: setting file URL:" << url;
+
+    if (m_selectUrl == url) {
+        fmDebug() << "Markdown preview: URL unchanged, skipping:" << url;
+        return true;
+    }
+
+    if (!url.isLocalFile()) {
+        fmWarning() << "Markdown preview: URL is not a local file:" << url;
+        return false;
+    }
+
+    const QString filePath = url.toLocalFile();
+    if (!QFileInfo::exists(filePath)) {
+        fmWarning() << "Markdown preview: file does not exist:" << filePath;
+        return false;
+    }
+
+    QFileInfo fileInfo(filePath);
+    qint64 fileSize = fileInfo.size();
+
+    if (fileSize <= 0) {
+        fmWarning() << "Markdown preview: file is empty or cannot determine size:" << filePath;
+        return false;
+    }
+
+    fmDebug() << "Markdown preview: file size:" << fileSize << "bytes, will read up to:" << kMaxReadSize << "bytes";
+
+    QFile file(filePath);
+    if (!file.open(QIODevice::ReadOnly | QIODevice::Text)) {
+        fmWarning() << "Markdown preview: failed to open file:" << filePath << "error:" << file.errorString();
+        return false;
+    }
+
+    // Limit read size to 5MB
+    qint64 readSize = qMin(fileSize, kMaxReadSize);
+    if (fileSize > kMaxReadSize) {
+        fmDebug() << "Markdown preview: file size exceeds limit, truncating to:" << kMaxReadSize << "bytes";
+    }
+
+    // Read file content
+    QByteArray data = file.read(readSize);
+    file.close();
+
+    if (data.isEmpty()) {
+        fmWarning() << "Markdown preview: failed to read file content:" << filePath;
+        return false;
+    }
+
+    // Convert to QString
+    const QString markdownContent = QString::fromUtf8(data);
+
+    // Create browser widget if not exists
+    if (!m_markdownBrowser) {
+        fmDebug() << "Markdown preview: creating new MarkdownContextWidget";
+        m_markdownBrowser = new MarkdownContextWidget;
+    }
+
+    // Set markdown content with base path for relative images
+    QString basePath = fileInfo.absolutePath();
+    m_markdownBrowser->markdownBrowser()->setMarkdownContent(markdownContent, basePath);
+
+    m_selectUrl = url;
+    m_titleStr = fileInfo.fileName();
+
+    fmInfo() << "Markdown preview: file loaded successfully:" << filePath << "title:" << m_titleStr;
+    Q_EMIT titleChanged();
+
+    return true;
+}
+
+QUrl MarkdownPreview::fileUrl() const
+{
+    return m_selectUrl;
+}
+
+QWidget *MarkdownPreview::contentWidget() const
+{
+    return m_markdownBrowser;
+}
+
+QString MarkdownPreview::title() const
+{
+    return m_titleStr;
+}
+
+bool MarkdownPreview::showStatusBarSeparator() const
+{
+    return false;
+}