Enable enumeration of writeback connectors if both libdrm and the device
support it. The new Card::has_writeback() method report if the card
support writeback connectors.

Existing code that expect all connectors to model an output may be
confused by the sudden availability of new connectors. To handle this
issue,

- add a KMSXX_DISABLE_WRITEBACK_CONNECTORS environment variable to
  disable enumeration of writeback connectors, similarly to universal
  planes ; and

- ignore writeback connectors where no specific connector is requested
  (Card::get_first_connected_connector(),
  ResourceManager::reserve_connector() if no connector name is
  specified, and applications that use all connected outputs).

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

Replace the hand-rolled draw_color_bar call in FlipState::draw_bar with
pixpat's "vbar" pattern via a new draw_vbar_pattern helper in kms++util.
The pattern fills the full buffer, so the old_xpos bookkeeping for
clearing the previous bar is no longer needed.

We can use std::format() and a custom print() wrapper with C++20. When
moving to C++23, we can drop the wrapper.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>

This commit addresses cppcheck warnings about mismatched printf format
specifiers (invalidPrintfArgType_sint). The format specifiers %i and %d
expect signed integers (int) but the variables being passed are unsigned
integers (uint32_t, unsigned). This mismatch can lead to undefined behavior
and incorrect output formatting.

Changes made:
- utils/kmstouch.cpp: Changed %i to %u for event code formatting
- utils/kmstouch.cpp: Changed %d to %u for event type and property type formatting
- utils/kmsview.cpp: Changed %d to %u for frame number formatting

These fixes ensure proper type safety in printf formatting and prevent
potential undefined behavior when printing unsigned integer values.

This commit addresses cppcheck warnings about member variables that are
not properly initialized in constructors (uninitMemberVar). Uninitialized
member variables can lead to undefined behavior and unpredictable program
execution, making this a critical bug fix.

Changes made:
- kmscube/cube-gles2.cpp: Initialize m_width and m_height to 0 in GlScene
  constructor to prevent undefined behavior when these values are used
- utils/kmstest.cpp: Initialize m_frame_num and m_flip_count to 0 in
  FlipState constructor to ensure proper frame counting behavior

These fixes prevent potential crashes and ensure deterministic behavior
by providing proper initial values for all member variables.

This commit addresses cppcheck warnings about C-style casts (cstyleCast)
by replacing them with appropriate C++ casts. C-style casts are considered
dangerous because they can perform unsafe conversions without compile-time
type checking, while C++ casts are more explicit and type-safe.

Changes made:
- static_cast for safe type conversions (e.g., void* to struct*)
- reinterpret_cast for pointer type conversions (e.g., uint8_t* to char*)
- Combined static_cast and reinterpret_cast for integer-to-pointer conversions

Fixed files:
- kmscube/cube-gles2.cpp: GLvoid* casts for OpenGL vertex attribute pointers
- kmscube/cube-wl.cpp: Wayland interface pointer casts
- kmscube/cube-x11.cpp: X11 window handle conversion
- utils/fbtest.cpp: mmap return value cast
- utils/kmstest.cpp: Framebuffer pointer arithmetic
- utils/kmsview.cpp: Framebuffer memory mapping cast

This commit addresses cppcheck warnings about variables that can be
declared as const references (constVariableReference). These variables
were being copied unnecessarily when they could be accessed as const
references, improving performance and code clarity.

Fixed files:
- kms++util/src/cpuframebuffer.cpp: Make plane reference const in destructor
- kms++util/src/testpat.cpp: Make info and lambda parameter const references
- utils/kmstest.cpp: Make loop variable const reference in output parsing

Fix cppcheck shadowVariable and shadowArgument warnings by renaming
local variables to avoid conflicts:
- Rename 'ob' to 'prop' in property creation loop in card.cpp
- Rename loop variable 'y_offset' to 'y_off' in conv-yuv-semiplanar.h
- Rename local 'y' to 'y_val' in SMPTE pattern generator in testpat.cpp
- Rename 'is_last' to 'child_is_last' in entry printing in kmsprint.cpp

These changes eliminate naming conflicts while preserving functionality
and improving code clarity.