fix(markdown): re-render preview on font change, fix hard breaks

- Font settings were read once at startup; connecting to
  fontNameChanged/fontSizeChanged signals ensures the preview
  re-renders whenever the user changes the editor font.
- Storing m_lastSourceText avoids re-parsing from the editor
  when only style needs to change.
- Single bare \n was treated as a soft break by CommonMark,
  collapsing agent output lines into one paragraph; injecting
  two trailing spaces converts them to hard breaks without
  touching fences or existing hard breaks.
- dockForTab now reads the QDockWidget pointer from tabData
  instead of matching by title, which was ambiguous when
  multiple docks shared the same windowTitle.
- AiAgentDock gets a 500px minimum width so it is usable
  when first docked.

Author: nullmastermind

src/MarkdownPreviewWidget.cpp

@@ -1,5 +1,6 @@
 #include "MarkdownPreviewWidget.h"
 #include "NotepadNextApplication.h"
+#include "ApplicationSettings.h"
 
 #include <QVBoxLayout>
 #include <QImage>
@@ -29,6 +30,10 @@ MarkdownPreviewWidget::MarkdownPreviewWidget(NotepadNextApplication *app, QWidge
 
     m_palette = app->palette();
     m_isDark = app->isEffectiveThemeDark();
+
+    auto *settings = app->getSettings();
+    connect(settings, &ApplicationSettings::fontNameChanged, this, &MarkdownPreviewWidget::onFontChanged);
+    connect(settings, &ApplicationSettings::fontSizeChanged, this, &MarkdownPreviewWidget::onFontChanged);
 }
 
 void MarkdownPreviewWidget::setContent(const QString &text, const QString &basePath)
@@ -69,6 +74,10 @@ MarkdownRenderRequest MarkdownPreviewWidget::buildRequest(const QString &text)
     req.isDark = m_isDark;
     req.basePath = m_basePath;
 
+    auto *settings = m_app->getSettings();
+    req.fontFamily = settings->fontName();
+    req.fontSize = settings->fontSize();
+
     QSet<QString> labels = MarkdownRenderer::scanFenceLabels(text);
     for (const QString &label : labels) {
         QString normalized = MarkdownRenderer::normalizeFenceLabel(label);
@@ -89,6 +98,7 @@ MarkdownRenderRequest MarkdownPreviewWidget::buildRequest(const QString &text)
 
 void MarkdownPreviewWidget::renderAsync(const QString &text)
 {
+    m_lastSourceText = text;
     int gen = m_renderGeneration.fetch_add(1, std::memory_order_relaxed) + 1;
     MarkdownRenderRequest req = buildRequest(text);
 
@@ -116,3 +126,9 @@ void MarkdownPreviewWidget::applyHtml(const QString &html)
     m_browser->setHtml(html);
     m_browser->verticalScrollBar()->setValue(scrollPos);
 }
+
+void MarkdownPreviewWidget::onFontChanged()
+{
+    if (m_cachedHtml.isEmpty()) return;
+    renderAsync(m_lastSourceText);
+}

src/MarkdownPreviewWidget.h

@@ -32,6 +32,7 @@ class MarkdownPreviewWidget : public PreviewContentWidget
     void renderAsync(const QString &text);
     void applyHtml(const QString &html);
     MarkdownRenderRequest buildRequest(const QString &text);
+    void onFontChanged();
 
     NotepadNextApplication *m_app;
     QTextBrowser *m_browser;
@@ -40,6 +41,7 @@ class MarkdownPreviewWidget : public PreviewContentWidget
     QPalette m_palette;
     bool m_isDark = false;
     QString m_cachedHtml;
+    QString m_lastSourceText;
     std::atomic<int> m_renderGeneration{0};
     QFutureWatcher<MarkdownRenderResult> *m_watcher = nullptr;
 

src/MarkdownRenderer.cpp

@@ -288,17 +288,26 @@ QString MarkdownRenderer::highlightCodeBlock(const QByteArray &code, const QStri
 
 // PLACEHOLDER_RENDER
 
-QString MarkdownRenderer::buildStyleBlock(const QPalette &palette, bool isDark)
+QString MarkdownRenderer::buildStyleBlock(const QPalette &palette, bool isDark,
+                                          const QString &fontFamily, int fontSize)
 {
     QString bg = palette.color(QPalette::Base).name();
     QString fg = palette.color(QPalette::Text).name();
     QString link = palette.color(QPalette::Link).name();
     QString mid = palette.color(QPalette::Mid).name();
     QString altBase = palette.color(QPalette::AlternateBase).name();
 
+    QString fontCss;
+    if (!fontFamily.isEmpty())
+        fontCss += QStringLiteral("font-family:'%1',system-ui,sans-serif;").arg(fontFamily);
+    else
+        fontCss += QStringLiteral("font-family:system-ui,sans-serif;");
+    if (fontSize > 0)
+        fontCss += QStringLiteral("font-size:%1pt;").arg(fontSize);
+
     return QStringLiteral(
         "<style>"
-        "body{background:%1;color:%2;font-family:system-ui,sans-serif;padding:16px;line-height:1.6;}"
+        "body{background:%1;color:%2;%6padding:16px;line-height:1.6;}"
         "a{color:%3;}"
         "code{background:%4;padding:2px 4px;border-radius:3px;font-family:monospace;}"
         "pre{background:%4;padding:12px;border-radius:4px;overflow-x:auto;}"
@@ -310,7 +319,7 @@ QString MarkdownRenderer::buildStyleBlock(const QPalette &palette, bool isDark)
         "hr{border:none;border-top:1px solid %5;}"
         "img{max-width:100%%;}"
         "</style>"
-    ).arg(bg, fg, link, altBase, mid);
+    ).arg(bg, fg, link, altBase, mid, fontCss);
 }
 
 namespace {
@@ -365,7 +374,7 @@ MarkdownRenderResult MarkdownRenderer::render(const MarkdownRenderRequest &reque
 
     ctx.html.reserve(ctx.sourceUtf8.size() * 2);
     ctx.html += QStringLiteral("<!DOCTYPE html><html><head>");
-    ctx.html += buildStyleBlock(request.palette, request.isDark);
+    ctx.html += buildStyleBlock(request.palette, request.isDark, request.fontFamily, request.fontSize);
     ctx.html += QStringLiteral("</head><body>");
 
     // Two-pass approach:

src/MarkdownRenderer.h

@@ -11,6 +11,8 @@ struct MarkdownRenderRequest {
     QPalette palette;
     bool isDark = false;
     QString basePath;
+    QString fontFamily;
+    int fontSize = 0;
 };
 
 struct MarkdownRenderResult {
@@ -29,7 +31,8 @@ class MarkdownRenderer
     static constexpr size_t kMaxHtmlBytes = 512 * 1024;
 
 private:
-    static QString buildStyleBlock(const QPalette &palette, bool isDark);
+    static QString buildStyleBlock(const QPalette &palette, bool isDark,
+                                    const QString &fontFamily, int fontSize);
     static QString highlightCodeBlock(const QByteArray &code, const QString &lexerName, bool isDark);
 };
 

src/docks/AiAgentDock.cpp

@@ -53,6 +53,7 @@ AiAgentDock::AiAgentDock(QString sessionId,
 {
     setAttribute(Qt::WA_DeleteOnClose, true);
     setObjectName(QStringLiteral("AiAgentDock_%1").arg(m_sessionId));
+    setMinimumWidth(500);
     // Spec ("Default dock area"): dock is unrestricted — user may move it to
     // any side. defaultArea() is only consulted on first attach.
     setAllowedAreas(Qt::AllDockWidgetAreas);

src/widgets/AcpMessageWidget.cpp

@@ -82,6 +82,40 @@ void normalizeBlockMargins(QTextDocument *doc)
     } while (cur.movePosition(QTextCursor::NextBlock));
 }
 
+// Agent output uses bare \n for visual line breaks, but CommonMark treats a
+// single newline as a soft break (rendered as a space). Convert lone \n into
+// hard breaks (two trailing spaces before the newline) so they render visually.
+// Preserves code fences, blank-line paragraph separators, and lines that
+// already end with trailing spaces or a backslash hard break.
+QString ensureHardBreaks(const QString &md)
+{
+    const QStringList lines = md.split(QLatin1Char('\n'));
+    QString out;
+    out.reserve(md.size() + lines.size() * 2);
+    bool inFence = false;
+
+    for (int i = 0; i < lines.size(); ++i) {
+        const QString &line = lines[i];
+
+        if (line.startsWith(QLatin1String("```")) || line.startsWith(QLatin1String("~~~"))) {
+            inFence = !inFence;
+        }
+
+        out += line;
+
+        if (i < lines.size() - 1) {
+            const bool nextIsBlank = (i + 1 < lines.size()) && lines[i + 1].trimmed().isEmpty();
+            const bool alreadyHard = line.endsWith(QLatin1String("  "))
+                                     || line.endsWith(QLatin1Char('\\'));
+            if (!inFence && !nextIsBlank && !line.trimmed().isEmpty() && !alreadyHard) {
+                out += QLatin1String("  ");
+            }
+            out += QLatin1Char('\n');
+        }
+    }
+    return out;
+}
+
 } // namespace
 
 AcpMessageWidget::AcpMessageWidget(QString role, QWidget *parent)
@@ -313,7 +347,7 @@ void AcpMessageWidget::rerender()
         // producing visible double borders. Re-emit the HTML with
         // cellspacing="0" so border-collapse actually collapses.
         QTextDocument tmp;
-        tmp.setMarkdown(m_text);
+        tmp.setMarkdown(ensureHardBreaks(m_text));
         QString html = tmp.toHtml();
         html.replace(QRegularExpression(QStringLiteral("<table([^>]*)>")),
                      QStringLiteral("<table\\1 cellspacing=\"0\" cellpadding=\"8\">"));
@@ -332,7 +366,7 @@ void AcpMessageWidget::rerender()
                                    || text.endsWith(QLatin1Char('\t')))) {
             text.chop(1);
         }
-        m_browser->document()->setMarkdown(text);
+        m_browser->document()->setMarkdown(ensureHardBreaks(text));
         normalizeBlockMargins(m_browser->document());
     } else {
         // Streamed chunks often end with "\n", which QTextDocument turns into

src/widgets/DockMiddleClickCloser.cpp

@@ -29,6 +29,7 @@
 #include <QStyle>
 #include <QStyleOptionDockWidget>
 #include <QTabBar>
+#include <QVariant>
 
 namespace {
 
@@ -85,14 +86,22 @@ Filter *sharedFilter()
     return instance.data();
 }
 
-// Finds the QDockWidget that owns a given tab in Qt's internal dock tab bar.
-// When QDockWidgets are tabified, Qt creates a QTabBar whose tab labels match
-// the docks' windowTitle(). We walk up to the nearest QMainWindow and search
-// its docks for a title match.
 QDockWidget *dockForTab(QTabBar *tabBar, int index)
 {
     if (index < 0)
         return nullptr;
+
+    // Qt stores the QDockWidget pointer (as quintptr) in each tab's data.
+    // This is the only unambiguous mapping when multiple docks share a title.
+    const QVariant data = tabBar->tabData(index);
+    if (data.isValid()) {
+        auto *widget = reinterpret_cast<QWidget *>(qvariant_cast<quintptr>(data));
+        if (auto *dock = qobject_cast<QDockWidget *>(widget))
+            return dock;
+    }
+
+    // Fallback: title match (ambiguous with duplicate titles, but covers the
+    // case where tabData is not populated).
     const QString tabText = tabBar->tabText(index);
     if (tabText.isEmpty())
         return nullptr;