fix: DCrumbEdit crumb 自适应容器宽度，修复缩小溢出与放大留白

src/widgets/dcrumbedit.cpp

@@ -554,22 +554,33 @@
     QWidget* widgetRight;
 };
 
 QSizeF CrumbObjectInterface::intrinsicSize(QTextDocument *doc, int posInDocument, const QTextFormat &format)
 {
-    Q_UNUSED(doc)
     Q_UNUSED(posInDocument)
 
     const DCrumbTextFormat crumb_format(format);
     const QFontMetricsF font_metrics(crumb_format.font());
     int radius = crumb_format.backgroundRadius();
 
-    if (crumb_format.tagColor().isValid())
-        return QSizeF(font_metrics.horizontalAdvance(crumb_format.text()) + font_metrics.height() + radius + 2, font_metrics.height() + 2);
+    if (crumb_format.tagColor().isValid()) {
+        qreal width = font_metrics.horizontalAdvance(crumb_format.text())
+                      + font_metrics.height() + radius + 2;
+        // 限制单个 crumb 不超过文档可用内容宽度，避免超宽标记撑开文档导致水平滚动条。
+        // 超宽时由 drawObject 做省略显示。仅对带标记颜色的 crumb 生效（本 issue 场景）。
+        const qreal textWidth = doc->textWidth();
+        if (textWidth > 0) {
+            const qreal avail = textWidth - 2 * doc->documentMargin();
+            if (avail > 0 && width > avail)
+                width = avail;
+        }
+        return QSizeF(width, font_metrics.height() + 2);
+    }
 
-    return QSizeF(font_metrics.horizontalAdvance(crumb_format.text()) + 2 * radius + 2, font_metrics.height() + 2 + TopMargin *2);
+    return QSizeF(font_metrics.horizontalAdvance(crumb_format.text()) + 2 * radius + 2,
+                  font_metrics.height() + 2 + TopMargin * 2);
 }
 
 void CrumbObjectInterface::drawObject(QPainter *painter, const QRectF &rect,
                                       QTextDocument *doc, int posInDocument, const QTextFormat &format)
 {
     Q_UNUSED(doc)
@@ -582,24 +593,32 @@
 
     QPainterPath background_path;
     QPainterPath tag_path;
-    const QRectF tag_rect(new_rect.x() + 2, new_rect.y() + 2, font_metrics.height() - 4, font_metrics.height() - 4);
+    const QRectF tag_rect(new_rect.x() + 2, new_rect.y() + 2,
+                          font_metrics.height() - 4, font_metrics.height() - 4);
 
     tag_path.addEllipse(tag_rect);
     background_path.addRoundedRect(new_rect, radius, crumb_format.backgroundRadius());
 
     painter->setRenderHint(QPainter::Antialiasing);
+    // 极窄宽度下色块可能超出收缩后的矩形，裁剪兜底防绘制越界
+    painter->save();
+    painter->setClipRect(new_rect);
     painter->fillPath(background_path, backgroundBrush(new_rect, crumb_format.background()));
 
     if (crumb_format.tagColor().isValid()) {
         painter->fillPath(tag_path, crumb_format.tagColor());
-
         painter->setPen(crumb_format.textColor());
-        painter->drawText(new_rect.adjusted(tag_rect.width() + 2, 0, -radius, 0),
-                          crumb_format.text(), Qt::AlignVCenter | Qt::AlignRight);
+        const QRectF textRect = new_rect.adjusted(tag_rect.width() + 2, 0, -radius, 0);
+        // intrinsicSize 已将超宽 crumb 收缩到可用宽度，此处按实际可用宽度省略文字
+        QString displayText = crumb_format.text();
+        if (font_metrics.horizontalAdvance(displayText) > textRect.width())
+            displayText = font_metrics.elidedText(displayText, Qt::ElideRight, textRect.width());
+        painter->drawText(textRect, displayText, Qt::AlignVCenter | Qt::AlignLeft);
     } else {
         painter->setPen(crumb_format.textColor());
         painter->drawText(new_rect, Qt::AlignCenter, crumb_format.text());
     }
+    painter->restore();
 }
 
 QBrush CrumbObjectInterface::backgroundBrush(const QRect &rect, const QBrush &brush)

tests/testcases/widgets/ut_dcrumbedit.cpp

@@ -3,11 +3,15 @@
 // SPDX-License-Identifier: LGPL-3.0-or-later
 
 #include <gtest/gtest.h>
 #include <QTest>
 #include <QClipboard>
 #include <QMimeData>
+#include <QTextDocument>
+#include <QAbstractTextDocumentLayout>
+#include <QPainter>
+#include <QImage>
 
 #include "dcrumbedit.h"
 #include <QDebug>
 
 DWIDGET_USE_NAMESPACE
@@ -104,3 +108,70 @@
     ASSERT_EQ(qApp->clipboard()->text(), "测试1 人物 测试2 儿童 测试3 照片 测试代码调试添加GTest");
     delete data;
 }
+
+// 验证：容器（文档）可用宽度小于 crumb 固有宽度时，带标记颜色的 crumb 文字会被省略且不溢出框外。
+// 对应 issue：放大缩小右侧边栏时预览区标记自适应不好（缩小溢出、放大留白）。
+TEST_F(ut_DCrumbedit, tagCrumbElidedAndNoOverflowWhenContainerNarrow)
+{
+    // 创建带标记颜色 + 超长文字的 crumb
+    DCrumbTextFormat format = edit->makeTextFormat(DCrumbEdit::red);
+    ASSERT_TRUE(format.tagColor().isValid());
+
+    const QString longText = QString::fromUtf8("标记文字").repeated(20); // 远超容器宽度的超长文字
+    format.setText(longText);
+    // 用纯色背景/文字，便于按像素检测绘制范围
+    format.setBackground(QBrush(Qt::yellow));
+    format.setTextColor(Qt::black);
+
+    ASSERT_TRUE(edit->appendCrumb(format));
+    ASSERT_EQ(edit->crumbList().size(), 1);
+    ASSERT_EQ(edit->crumbList().first(), longText);
+
+    QTextDocument *doc = edit->document();
+    const QFontMetricsF fm(format.font());
+    // crumb 固有宽度（与 intrinsicSize 口径一致）
+    const qreal intrinsicWidth =
+        fm.horizontalAdvance(longText) + fm.height() + format.backgroundRadius() + 2;
+    // 将文档可用宽度设为远小于固有宽度，模拟缩小侧边栏
+    const int narrowWidth = int(intrinsicWidth / 3);
+    ASSERT_GT(narrowWidth, 0);
+    ASSERT_LT(qreal(narrowWidth), intrinsicWidth);
+    doc->setTextWidth(narrowWidth);
+
+    // 修复前 intrinsicSize 未限宽，单个超宽 crumb 会撑开文档宽度导致水平滚动条；
+    // 修复后 idealWidth 应不超出文档可用宽度。
+    EXPECT_LE(doc->idealWidth(), qreal(narrowWidth))
+        << "单个超宽 crumb 撑开了文档宽度(" << doc->idealWidth()
+        << " > " << narrowWidth << ")，会产生水平滚动条";
+
+    // 渲染文档到一张比 narrowWidth 更宽的图片，检测 crumb 是否溢出文档可用宽度
+    QImage img(int(intrinsicWidth) + 40, 100, QImage::Format_ARGB32);
+    img.fill(Qt::white);
+    QPainter p(&img);
+    QAbstractTextDocumentLayout::PaintContext ctx;
+    doc->documentLayout()->draw(&p, ctx);
+    p.end();
+
+    // 找出最右侧的非背景像素，crumb 不应溢出到 narrowWidth 右侧（留少量抗锯齿容差）
+    int rightMostContentX = -1;
+    for (int y = 0; y < img.height(); ++y) {
+        for (int x = img.width() - 1; x > rightMostContentX; --x) {
+            if (img.pixelColor(x, y) != Qt::white) {
+                rightMostContentX = x;
+                break;
+            }
+        }
+    }
+    // 容差 8 像素用于抗锯齿/圆角；无修复时 crumb 会溢出到约 intrinsicWidth 处
+    EXPECT_LT(rightMostContentX, narrowWidth + 8)
+        << "crumb 内容溢出文档可用宽度(" << narrowWidth
+        << ")，rightMostContentX=" << rightMostContentX;
+
+    // 绘制层省略不改变实际 crumb 文本
+    EXPECT_EQ(edit->crumbList().first(), longText);
+
+    // 省略逻辑：对窄宽度做 elidedText 应得到含省略号的较短文本
+    const QString elided = fm.elidedText(longText, Qt::ElideRight, narrowWidth);
+    EXPECT_LT(fm.horizontalAdvance(elided), fm.horizontalAdvance(longText));
+    EXPECT_TRUE(elided.contains(QChar(0x2026))); // 包含省略号 “…”
+}