PyQt5/PyQt6 Compatibility Implementation

The plugin features a PyQt5/PyQt6 compatibility implementation trying to make it work across different QGIS installations using either PyQt5 or PyQt6. The compatibility layer should be dropped when QGIS fully transitions to PyQt6.

Overview

The PyQt5/PyQt6 compatibility layer detects the PyQt version at runtime and provides unified interfaces for PyQt-specific functionality.

Some Differences Between PyQt5 and PyQt6

QVariant changes: In PyQt6, QVariant is deprecated and Python native types are used instead
QMetaType changes: API restructuring with nested enum access patterns
Dialog result constants: Moved from class attributes to enum values (QDialog.Accepted → QDialog.DialogCode.Accepted)
Cursor shape constants: Restructured into nested enums (Qt.ArrowCursor → Qt.CursorShape.ArrowCursor)
Enum structure: Proper Python enums in PyQt6 vs class attributes in PyQt5

Compatibility Module Implementation

Core Implementation

The main compatibility logic is implemented in dip_strike_tools/toolbelt/qt_compat.py, which provides:

Runtime PyQt version detection: Automatically detects whether PyQt5 or PyQt6 is being used
QVariant compatibility: Handles the deprecation of QVariant in PyQt6
QMetaType compatibility: Provides unified access to type constants
Dialog result constants: Unified access to dialog result values
Cursor shape constants: Handles enum structure changes in PyQt6

Key Components

1. Version Detection

from dip_strike_tools.toolbelt import IS_PYQT5, IS_PYQT6, get_qt_version_info

# Runtime detection
if IS_PYQT6:
    # PyQt6 specific code
else:
    # PyQt5 specific code

# Get detailed version info
info = get_qt_version_info()

2. QVariant Compatibility

from dip_strike_tools.toolbelt import QVariant, qvariant_cast

# Use QVariant types consistently
field.setType(QVariant.Double)  # Works in both PyQt5 and PyQt6
field.setType(QVariant.String)  # Works in both PyQt5 and PyQt6

# Cast values safely
value = qvariant_cast(raw_value, QVariant.Double)

3. QMetaType Compatibility

from dip_strike_tools.toolbelt import QMetaTypeWrapper as QMetaType

# Use QMetaType consistently
field.setType(QMetaType.Double)   # Works in both versions
field.setType(QMetaType.QString)  # Works in both versions

4. Dialog Result Constants

from dip_strike_tools.toolbelt import DIALOG_ACCEPTED, DIALOG_REJECTED

# Check dialog results consistently
if dialog.result() == DIALOG_ACCEPTED:
    # Handle accepted dialog
elif dialog.result() == DIALOG_REJECTED:
    # Handle rejected dialog

5. Enhanced Enum Handling

from dip_strike_tools.toolbelt import enum_value, get_dialog_result

# Generic enum value access
value = enum_value(SomeEnum, "ValueName")

# Specific dialog result handling
accepted = get_dialog_result(QDialog, "Accepted")  # Works in both PyQt5/6

Usage Patterns

Field Type Setting

from dip_strike_tools.toolbelt import QMetaTypeWrapper as QMetaType

# Create a field with double type
field = QgsField()
field.setName("value_field")
field.setType(QMetaType.Double)  # Works in both PyQt5/6

Value Handling

from dip_strike_tools.toolbelt import QVariant, qvariant_cast

# Safe value extraction
def extract_value(qvariant_value):
    if qvariant_value is None:
        return None
    elif isinstance(qvariant_value, QVariant):
        if qvariant_value.isNull():
            return None
        else:
            return qvariant_value.value()
    else:
        return qvariant_value

Type Checking

from dip_strike_tools.toolbelt import QVariant

# Check field types consistently
if field.type() == QVariant.Double:
    # Handle double field
elif field.type() == QVariant.String:
    # Handle string field

Maintenance

When adding new PyQt-dependent code:

Import from toolbelt: Use compatibility imports instead of direct PyQt imports
Check compatibility module: Add new compatibility patterns if needed
Test both versions: Ensure new code works with both PyQt5 and PyQt6
Update documentation: Document any new compatibility patterns