优化单图模式下标题的显示位置居中 (#4485)

* 当图片格式设置为single时，图片居中显示。

* 优化单图模式下标题的显示位置优化了标题威之居中

app/src/main/java/io/legado/app/ui/book/read/page/provider/TextChapterLayout.kt

@@ -194,6 +194,7 @@ class TextChapterLayout(
                     titlePaint,
                     titlePaintTextHeight,
                     titlePaintFontMetrics,
+                    book.getImageStyle(),
                     isTitle = true,
                     emptyContent = contents.isEmpty(),
                     isVolumeTitle = bookChapter.isVolume
@@ -231,6 +232,7 @@ class TextChapterLayout(
                     contentPaint,
                     contentPaintTextHeight,
                     contentPaintFontMetrics,
+                    book.getImageStyle(),
                     srcList = srcList
                 ).let {
                     absStartX = it.first
@@ -250,7 +252,8 @@ class TextChapterLayout(
                             text,
                             contentPaint,
                             contentPaintTextHeight,
-                            contentPaintFontMetrics
+                            contentPaintFontMetrics,
+                            book.getImageStyle()
                         ).let {
                             absStartX = it.first
                             durY = it.second
@@ -278,7 +281,8 @@ class TextChapterLayout(
                             if (AppConfig.enableReview) text + ChapterProvider.reviewChar else text,
                             contentPaint,
                             contentPaintTextHeight,
-                            contentPaintFontMetrics
+                            contentPaintFontMetrics,
+                            book.getImageStyle()
                         ).let {
                             absStartX = it.first
                             durY = it.second
@@ -443,6 +447,7 @@ class TextChapterLayout(
         textPaint: TextPaint,
         textHeight: Float,
         fontMetrics: Paint.FontMetrics,
+        imageStyle: String?,
         isTitle: Boolean = false,
         emptyContent: Boolean = false,
         isVolumeTitle: Boolean = false,
@@ -487,8 +492,31 @@ class TextChapterLayout(
                 }
             }
 
-            isTitle && textPages.isEmpty() && pendingTextPage.lines.isEmpty() ->
-                y + titleTopSpacing
+            isTitle && textPages.isEmpty() && pendingTextPage.lines.isEmpty() -> {
+                when (imageStyle?.uppercase(Locale.ROOT)) {
+                    Book.imgStyleSingle -> {
+                        val textPage = pendingTextPage
+                        if (textPage.lineSize == 0) {
+                            val ty = (visibleHeight - layout.lineCount * textHeight) / 2
+                            if (ty > titleTopSpacing) ty else titleTopSpacing.toFloat()
+                        } else {
+                            var textLayoutHeight = layout.lineCount * textHeight
+                            val fistLine = textPage.getLine(0)
+                            if (fistLine.lineTop < textLayoutHeight + titleTopSpacing) {
+                                textLayoutHeight = fistLine.lineTop - titleTopSpacing
+                            }
+                            textPage.lines.forEach {
+                                it.lineTop -= textLayoutHeight
+                                it.lineBase -= textLayoutHeight
+                                it.lineBottom -= textLayoutHeight
+                            }
+                            y - textLayoutHeight
+                        }
+                    }
+
+                    else -> y + titleTopSpacing
+                }
+            }
 
             else -> y
         }
@@ -539,7 +567,7 @@ class TextChapterLayout(
                     //标题x轴居中
                     val startX = if (
                         isTitle &&
-                        (ReadBookConfig.isMiddleTitle || emptyContent || isVolumeTitle)
+                        (ReadBookConfig.isMiddleTitle || emptyContent || isVolumeTitle || imageStyle == "SINGLE")
                     ) {
                         (visibleWidth - desiredWidth) / 2
                     } else {
@@ -554,7 +582,7 @@ class TextChapterLayout(
                 else -> {
                     if (
                         isTitle &&
-                        (ReadBookConfig.isMiddleTitle || emptyContent || isVolumeTitle)
+                        (ReadBookConfig.isMiddleTitle || emptyContent || isVolumeTitle || imageStyle == "SINGLE")
                     ) {
                         //标题居中
                         val startX = (visibleWidth - desiredWidth) / 2