fix: scale task manager preview icons for high DPI displays

[wjyrich]

1. Added device pixel ratio scaling to icon size calculation
2. This ensures icons appear sharp and properly sized on high DPI screens
3. Previously used fixed PREVIEW_TITLE_HEIGHT resulted in blurry icons on high DPI displays
4. Now scales the icon pixmap according to the device's pixel ratio

fix: 为高DPI显示器缩放任务管理器预览图标

1. 在图标尺寸计算中添加设备像素比缩放
2. 确保在高DPI屏幕上图标显示清晰且尺寸正确
3. 之前使用的固定PREVIEW_TITLE_HEIGHT在高DPI显示器上会导致图标模糊
4. 现在根据设备的像素比缩放图标像素图

PMS: BUG-336089

Summary by Sourcery

Bug Fixes:

• Replace fixed PREVIEW_TITLE_HEIGHT with a size scaled by qApp->devicePixelRatio to prevent blurry icons on high DPI screens.

[sourcery-ai]

Reviewer's guide (collapsed on small PRs)

Reviewer's Guide

Introduces DPI-aware scaling when generating task manager preview icons by computing and applying a scaled size based on the device pixel ratio, replacing the previous fixed-height approach to ensure sharp rendering on high-DPI displays.

Sequence diagram for DPI-aware icon rendering in task manager preview

sequenceDiagram
participant "X11WindowPreviewContainer"
participant "QIcon"
participant "QApplication"
participant "Device"

"X11WindowPreviewContainer"->>"QApplication": get devicePixelRatio()
"QApplication"->>"Device": query pixel ratio
"Device"-->>"QApplication": return pixel ratio
"QApplication"-->>"X11WindowPreviewContainer": return pixel ratio
"X11WindowPreviewContainer"->>"QIcon": request icon pixmap with scaled size
"QIcon"-->>"X11WindowPreviewContainer": return scaled pixmap

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Class diagram for updated icon scaling in X11WindowPreviewContainer

classDiagram
class X11WindowPreviewContainer {
  +void updatePreviewIconFromString(QString stringData)
}
class QApplication {
  +double devicePixelRatio()
}
class QIcon {
  +QPixmap pixmap(int width, int height)
}
X11WindowPreviewContainer --> QApplication : uses
X11WindowPreviewContainer --> QIcon : uses

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File-Level Changes

Change	Details	Files
Enabled DPI-aware scaling for task manager preview icons	Compute scaledSize as PREVIEW_TITLE_HEIGHT multiplied by the app’s devicePixelRatio() Use scaledSize for the QIcon::pixmap() call instead of the fixed PREVIEW_TITLE_HEIGHT	panels/dock/taskmanager/x11preview.cpp

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[sourcery-ai]

Hey there - I've reviewed your changes and they look great!

Prompt for AI Agents

Please address the comments from this code review:

## Individual Comments

### Comment 1
<location> `panels/dock/taskmanager/x11preview.cpp:773-774` </location>
<code_context>
     } else {
         // is (likely) icon name from theme
-        pix = QIcon::fromTheme(stringData).pixmap(PREVIEW_TITLE_HEIGHT, PREVIEW_TITLE_HEIGHT);
+        const int scaledSize = PREVIEW_TITLE_HEIGHT * qApp->devicePixelRatio();
+        pix = QIcon::fromTheme(stringData).pixmap(scaledSize, scaledSize);
     }

</code_context>

<issue_to_address>
**suggestion:** Consider using qRound or qCeil for scaledSize to avoid fractional pixel values.

Multiplying by devicePixelRatio() can produce non-integer values, which may cause issues with pixmap(). Applying qRound or qCeil will ensure scaledSize is always an integer, leading to more reliable rendering.

```suggestion
#include <QtMath>
        const int scaledSize = qRound(PREVIEW_TITLE_HEIGHT * qApp->devicePixelRatio());
        pix = QIcon::fromTheme(stringData).pixmap(scaledSize, scaledSize);
```
</issue_to_address>

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[deepin-ci-robot]

deepin pr auto review

这是一个关于窗口预览图标显示的改进，主要涉及高DPI显示的适配。让我来分析这个改动：

1. 语法逻辑：

• 语法正确，符合C++标准
• 逻辑清晰，添加了对设备像素比(devicePixelRatio)的考虑

2. 代码质量改进：

• 添加了const限定符，保证scaledSize不会被意外修改，提高了代码的安全性
• 使用有意义的变量名scaledSize，提高了代码可读性
• 保持了原有的错误处理逻辑(pix.isNull())

3. 性能优化：

• 这个改动实际上是在显示质量上做优化，而不是性能
• 对于高DPI显示器，现在会生成更清晰的图标
• 计算devicePixelRatio的开销很小，对性能影响微乎其微

4. 安全性改进：

• 使用qApp->devicePixelRatio()获取系统缩放比例，比硬编码更安全
• 保持了原有的错误处理机制，确保在图标加载失败时有适当的处理

建议：

1. 可以考虑添加注释说明为什么要考虑devicePixelRatio，帮助其他开发者理解这个改动
2. 如果PREVIEW_TITLE_HEIGHT是一个宏定义，可以考虑将其改为constexpr常量，以提高类型安全性

总的来说，这是一个很好的改进，主要解决了在高DPI显示器上图标模糊的问题，代码质量也有所提升。

[deepin-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: BLumia, wjyrich

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