/mnt/nas/libepaper/include/epaper/drivers/capabilities.hpp

Check if a driver supports a specific display mode at compile-time.

Check if a driver supports a specific display mode at compile-time.Uses driver_traits specialization to determine mode compatibility.

Support Logic:

• BlackWhite: Always supported (baseline mode for all e-paper)
• Grayscale4: Requires driver_traits<Driver>::supports_grayscale == true
• BWR/BWY/Spectra6: Requires exact match with driver_traits<Driver>::max_mode

Why Exact Match for Color Modes? Color modes are hardware-specific and mutually exclusive:

• BWR (Red) ≠ BWY (Yellow) - different ink formulations
• Spectra6 ≠ BWR - incompatible command sets Using <= comparison would falsely suggest BWR(2) < Spectra6(4) implies compatibility.

Rationale:

• Prevents runtime mode validation errors
• Enables compile-time specialization (e.g., if constexpr)
• Clear error messages at template instantiation

Template Parameters

Driver

Driver type to query (must satisfy DriverTraits)

Parameters

mode	Display mode to check

Returns

true if driver supports the mode, false otherwise

// Compile-time mode validation
if constexpr (supports_display_mode<EPD27>(DisplayMode::BWR)) {
  auto display = create_display<EPD27>(device, DisplayMode::BWR);
} else {
  auto display = create_display<EPD27>(device, DisplayMode::BlackWhite);
}
 
// Static assertion for required mode
static_assert(supports_display_mode<MyDriver>(DisplayMode::Grayscale4),
              "This app requires grayscale support");

See also

driver_traits, DisplayMode, create_display()

#pragma once
 
#include "epaper/drivers/driver.hpp"
#include <concepts>
#include <cstddef>
 
namespace epaper {
 
template <typename Driver> struct driver_traits;
// Base template is empty/undefined to force specialization
// Or we can leave it undefined so it fails instantiation if not specialized.
 
template <typename T>
concept DriverTraits = requires {
  requires std::convertible_to<decltype(driver_traits<T>::max_mode), DisplayMode>;
  requires std::convertible_to<decltype(driver_traits<T>::supports_grayscale), bool>;
  requires std::convertible_to<decltype(driver_traits<T>::supports_partial_refresh), bool>;
  requires std::convertible_to<decltype(driver_traits<T>::supports_power_control), bool>;
  requires std::convertible_to<decltype(driver_traits<T>::supports_wake_from_sleep), bool>;
  requires std::convertible_to<decltype(driver_traits<T>::max_width), std::size_t>;
  requires std::convertible_to<decltype(driver_traits<T>::max_height), std::size_t>;
};
 
template <typename Driver>
  requires DriverTraits<Driver>
[[nodiscard]] constexpr auto supports_display_mode(DisplayMode mode) noexcept -> bool {
  // Always support single-bit BW
  if (mode == DisplayMode::BlackWhite) {
    return true;
  }
 
  // Grayscale support is explicit
  if (mode == DisplayMode::Grayscale4) {
    return driver_traits<Driver>::supports_grayscale;
  }
 
  // For color modes (BWR, BWY, Spectra6), strict matching is required.
  // Inequality (<=) is unsafe because modes like BWR(2) and BWY(3) are mutually exclusive,
  // not hierarchical. A Spectra6(5) driver might not support legacy BWR(2) commands.
  return mode == driver_traits<Driver>::max_mode;
}
 
} // namespace epaper