[feature] Support horizontal alignment in HTML labels

For multi-line labels, this allows use of either:

- HTML <p align="xxx"> attributes
- CSS "text-align: xxx"
- HTML <center>some text</center> tags

Supported alignments are left, right, center and justify

Horizontal alignment can be used in all contexts where
HTML text is rendered, EXCEPT for curved labels (since they
are restricted to single-line text)

Sponsored by City of Freiburg im Breisgau

python/PyQt6/core/auto_additions/qgstextblockformat.py

@@ -0,0 +1,17 @@
+# The following has been generated automatically from src/core/textrenderer/qgstextblockformat.h
+# monkey patching scoped based enum
+QgsTextBlockFormat.BooleanValue.NotSet.__doc__ = "Property is not set"
+QgsTextBlockFormat.BooleanValue.SetTrue.__doc__ = "Property is set and ``True``"
+QgsTextBlockFormat.BooleanValue.SetFalse.__doc__ = "Property is set and ``False``"
+QgsTextBlockFormat.BooleanValue.__doc__ = """Status values for boolean format properties
+
+* ``NotSet``: Property is not set
+* ``SetTrue``: Property is set and ``True``
+* ``SetFalse``: Property is set and ``False``
+
+"""
+# --
+try:
+    QgsTextBlockFormat.__group__ = ['textrenderer']
+except NameError:
+    pass

python/PyQt6/core/auto_generated/textrenderer/qgstextblock.sip.in

@@ -72,6 +72,24 @@ Returns ``True`` if the block is empty.
     int size() const;
 %Docstring
 Returns the number of fragments in the block.
+%End
+
+    const QgsTextBlockFormat &blockFormat() const;
+%Docstring
+Returns the block formatting for the fragment.
+
+.. seealso:: :py:func:`setBlockFormat`
+
+.. versionadded:: 3.40
+%End
+
+    void setBlockFormat( const QgsTextBlockFormat &format );
+%Docstring
+Sets the block ``format`` for the fragment.
+
+.. seealso:: :py:func:`blockFormat`
+
+.. versionadded:: 3.40
 %End
 
     void applyCapitalization( Qgis::Capitalization capitalization );

python/PyQt6/core/auto_generated/textrenderer/qgstextblockformat.sip.in

@@ -0,0 +1,123 @@
+/************************************************************************
+ * This file has been generated automatically from                      *
+ *                                                                      *
+ * src/core/textrenderer/qgstextblockformat.h                           *
+ *                                                                      *
+ * Do not edit manually ! Edit header and run scripts/sipify.py again   *
+ ************************************************************************/
+
+
+
+
+
+class QgsTextBlockFormat
+{
+%Docstring(signature="appended")
+Stores information relating to individual block formatting.
+
+These options encapsulate formatting options which override the default
+settings from a :py:class:`QgsTextFormat` for individual text blocks.
+
+.. warning::
+
+   This API is not considered stable and may change in future QGIS versions.
+
+.. versionadded:: 3.40
+%End
+
+%TypeHeaderCode
+#include "qgstextblockformat.h"
+%End
+  public:
+
+    QgsTextBlockFormat();
+
+    QgsTextBlockFormat( const QTextBlockFormat &format );
+%Docstring
+Constructor for QgsTextBlockFormat, based on the specified QTextBlockFormat ``format``.
+%End
+
+    enum class BooleanValue
+    {
+      NotSet,
+      SetTrue,
+      SetFalse,
+    };
+
+    void overrideWith( const QgsTextBlockFormat &other );
+%Docstring
+Override all the default/unset properties of the current block format
+with the settings from another format.
+
+This will replace any default/unset existing settings with the
+settings from ``other``.
+
+Any settings which are default/unset in ``other`` will be left unchanged.
+
+:param other: The format to override with.
+%End
+
+    bool hasHorizontalAlignmentSet() const;
+%Docstring
+Returns ``True`` if the format has an explicit horizontal alignment set.
+
+If ``False`` is returned then the horizontal alignment will be inherited.
+
+.. seealso:: :py:func:`setHasHorizontalAlignmentSet`
+
+.. seealso:: :py:func:`horizontalAlignment`
+%End
+
+    void setHasHorizontalAlignmentSet( bool set );
+%Docstring
+Sets whether the format has an explicit horizontal alignment ``set``.
+
+If ``set`` is ``False`` then the horizontal alignment will be inherited.
+
+.. seealso:: :py:func:`hasHorizontalAlignmentSet`
+
+.. seealso:: :py:func:`setHorizontalAlignment`
+%End
+
+    Qgis::TextHorizontalAlignment horizontalAlignment() const;
+%Docstring
+Returns the format horizontal alignment.
+
+This property is only respected if :py:func:`~QgsTextBlockFormat.hasHorizontalAlignmentSet` is ``True``.
+
+.. seealso:: :py:func:`hasHorizontalAlignmentSet`
+
+.. seealso:: :py:func:`setHorizontalAlignment`
+%End
+
+    void setHorizontalAlignment( Qgis::TextHorizontalAlignment alignment );
+%Docstring
+Sets the format horizontal ``alignment``.
+
+This property is only respected if :py:func:`~QgsTextBlockFormat.hasHorizontalAlignmentSet` is ``True``.
+
+.. seealso:: :py:func:`hasHorizontalAlignmentSet`
+
+.. seealso:: :py:func:`horizontalAlignment`
+%End
+
+    void updateFontForFormat( QFont &font, const QgsRenderContext &context, double scaleFactor = 1.0 ) const;
+%Docstring
+Updates the specified ``font`` in place, applying block formatting options which
+are applicable on a font level when rendered in the given ``context``.
+
+The optional ``scaleFactor`` parameter can specify a font size scaling factor. It is recommended to set this to
+:py:func:`QgsTextRenderer.calculateScaleFactorForFormat()` and then manually calculations
+based on the resultant font metrics. Failure to do so will result in poor quality text rendering
+at small font sizes.
+%End
+
+};
+
+/************************************************************************
+ * This file has been generated automatically from                      *
+ *                                                                      *
+ * src/core/textrenderer/qgstextblockformat.h                           *
+ *                                                                      *
+ * Do not edit manually ! Edit header and run scripts/sipify.py again   *
+ ************************************************************************/

python/PyQt6/core/core_auto.sip

@@ -726,6 +726,7 @@
 %Include auto_generated/textrenderer/qgsfontmanager.sip
 %Include auto_generated/textrenderer/qgstextbackgroundsettings.sip
 %Include auto_generated/textrenderer/qgstextblock.sip
+%Include auto_generated/textrenderer/qgstextblockformat.sip
 %Include auto_generated/textrenderer/qgstextbuffersettings.sip
 %Include auto_generated/textrenderer/qgstextcharacterformat.sip
 %Include auto_generated/textrenderer/qgstextdocument.sip

python/core/auto_additions/qgstextblockformat.py

@@ -0,0 +1,17 @@
+# The following has been generated automatically from src/core/textrenderer/qgstextblockformat.h
+# monkey patching scoped based enum
+QgsTextBlockFormat.BooleanValue.NotSet.__doc__ = "Property is not set"
+QgsTextBlockFormat.BooleanValue.SetTrue.__doc__ = "Property is set and ``True``"
+QgsTextBlockFormat.BooleanValue.SetFalse.__doc__ = "Property is set and ``False``"
+QgsTextBlockFormat.BooleanValue.__doc__ = """Status values for boolean format properties
+
+* ``NotSet``: Property is not set
+* ``SetTrue``: Property is set and ``True``
+* ``SetFalse``: Property is set and ``False``
+
+"""
+# --
+try:
+    QgsTextBlockFormat.__group__ = ['textrenderer']
+except NameError:
+    pass

python/core/auto_generated/textrenderer/qgstextblock.sip.in

@@ -72,6 +72,24 @@ Returns ``True`` if the block is empty.
     int size() const;
 %Docstring
 Returns the number of fragments in the block.
+%End
+
+    const QgsTextBlockFormat &blockFormat() const;
+%Docstring
+Returns the block formatting for the fragment.
+
+.. seealso:: :py:func:`setBlockFormat`
+
+.. versionadded:: 3.40
+%End
+
+    void setBlockFormat( const QgsTextBlockFormat &format );
+%Docstring
+Sets the block ``format`` for the fragment.
+
+.. seealso:: :py:func:`blockFormat`
+
+.. versionadded:: 3.40
 %End
 
     void applyCapitalization( Qgis::Capitalization capitalization );

python/core/auto_generated/textrenderer/qgstextblockformat.sip.in

@@ -0,0 +1,123 @@
+/************************************************************************
+ * This file has been generated automatically from                      *
+ *                                                                      *
+ * src/core/textrenderer/qgstextblockformat.h                           *
+ *                                                                      *
+ * Do not edit manually ! Edit header and run scripts/sipify.py again   *
+ ************************************************************************/
+
+
+
+
+
+class QgsTextBlockFormat
+{
+%Docstring(signature="appended")
+Stores information relating to individual block formatting.
+
+These options encapsulate formatting options which override the default
+settings from a :py:class:`QgsTextFormat` for individual text blocks.
+
+.. warning::
+
+   This API is not considered stable and may change in future QGIS versions.
+
+.. versionadded:: 3.40
+%End
+
+%TypeHeaderCode
+#include "qgstextblockformat.h"
+%End
+  public:
+
+    QgsTextBlockFormat();
+
+    QgsTextBlockFormat( const QTextBlockFormat &format );
+%Docstring
+Constructor for QgsTextBlockFormat, based on the specified QTextBlockFormat ``format``.
+%End
+
+    enum class BooleanValue
+    {
+      NotSet,
+      SetTrue,
+      SetFalse,
+    };
+
+    void overrideWith( const QgsTextBlockFormat &other );
+%Docstring
+Override all the default/unset properties of the current block format
+with the settings from another format.
+
+This will replace any default/unset existing settings with the
+settings from ``other``.
+
+Any settings which are default/unset in ``other`` will be left unchanged.
+
+:param other: The format to override with.
+%End
+
+    bool hasHorizontalAlignmentSet() const;
+%Docstring
+Returns ``True`` if the format has an explicit horizontal alignment set.
+
+If ``False`` is returned then the horizontal alignment will be inherited.
+
+.. seealso:: :py:func:`setHasHorizontalAlignmentSet`
+
+.. seealso:: :py:func:`horizontalAlignment`
+%End
+
+    void setHasHorizontalAlignmentSet( bool set );
+%Docstring
+Sets whether the format has an explicit horizontal alignment ``set``.
+
+If ``set`` is ``False`` then the horizontal alignment will be inherited.
+
+.. seealso:: :py:func:`hasHorizontalAlignmentSet`
+
+.. seealso:: :py:func:`setHorizontalAlignment`
+%End
+
+    Qgis::TextHorizontalAlignment horizontalAlignment() const;
+%Docstring
+Returns the format horizontal alignment.
+
+This property is only respected if :py:func:`~QgsTextBlockFormat.hasHorizontalAlignmentSet` is ``True``.
+
+.. seealso:: :py:func:`hasHorizontalAlignmentSet`
+
+.. seealso:: :py:func:`setHorizontalAlignment`
+%End
+
+    void setHorizontalAlignment( Qgis::TextHorizontalAlignment alignment );
+%Docstring
+Sets the format horizontal ``alignment``.
+
+This property is only respected if :py:func:`~QgsTextBlockFormat.hasHorizontalAlignmentSet` is ``True``.
+
+.. seealso:: :py:func:`hasHorizontalAlignmentSet`
+
+.. seealso:: :py:func:`horizontalAlignment`
+%End
+
+    void updateFontForFormat( QFont &font, const QgsRenderContext &context, double scaleFactor = 1.0 ) const;
+%Docstring
+Updates the specified ``font`` in place, applying block formatting options which
+are applicable on a font level when rendered in the given ``context``.
+
+The optional ``scaleFactor`` parameter can specify a font size scaling factor. It is recommended to set this to
+:py:func:`QgsTextRenderer.calculateScaleFactorForFormat()` and then manually calculations
+based on the resultant font metrics. Failure to do so will result in poor quality text rendering
+at small font sizes.
+%End
+
+};
+
+/************************************************************************
+ * This file has been generated automatically from                      *
+ *                                                                      *
+ * src/core/textrenderer/qgstextblockformat.h                           *
+ *                                                                      *
+ * Do not edit manually ! Edit header and run scripts/sipify.py again   *
+ ************************************************************************/

python/core/core_auto.sip

@@ -726,6 +726,7 @@
 %Include auto_generated/textrenderer/qgsfontmanager.sip
 %Include auto_generated/textrenderer/qgstextbackgroundsettings.sip
 %Include auto_generated/textrenderer/qgstextblock.sip
+%Include auto_generated/textrenderer/qgstextblockformat.sip
 %Include auto_generated/textrenderer/qgstextbuffersettings.sip
 %Include auto_generated/textrenderer/qgstextcharacterformat.sip
 %Include auto_generated/textrenderer/qgstextdocument.sip

src/core/CMakeLists.txt

@@ -359,6 +359,7 @@ set(QGIS_CORE_SRCS
   textrenderer/qgsfontmanager.cpp
   textrenderer/qgstextbackgroundsettings.cpp
   textrenderer/qgstextblock.cpp
+  textrenderer/qgstextblockformat.cpp
   textrenderer/qgstextbuffersettings.cpp
   textrenderer/qgstextcharacterformat.cpp
   textrenderer/qgstextdocument.cpp
@@ -1981,6 +1982,7 @@ set(QGIS_CORE_HDRS
   textrenderer/qgsfontmanager.h
   textrenderer/qgstextbackgroundsettings.h
   textrenderer/qgstextblock.h
+  textrenderer/qgstextblockformat.h
   textrenderer/qgstextbuffersettings.h
   textrenderer/qgstextcharacterformat.h
   textrenderer/qgstextdocument.h

src/core/textrenderer/qgstextblock.cpp

@@ -86,6 +86,11 @@ int QgsTextBlock::size() const
   return mFragments.size();
 }
 
+void QgsTextBlock::setBlockFormat( const QgsTextBlockFormat &format )
+{
+  mBlockFormat = format;
+}
+
 void QgsTextBlock::applyCapitalization( Qgis::Capitalization capitalization )
 {
   for ( QgsTextFragment &fragment : mFragments )