TouchInputMapper: Use a fixed scale factor for external drawing tablets am: 7d9cb5a6

            : ui::Transform();

    // Step 4: Scale the raw coordinates to the display space.

    // - Here, we assume that the raw surface of the touch device maps perfectly to the surface

    //   of the display panel. This is usually true for touchscreens.

    // - In DIRECT mode, we assume that the raw surface of the touch device maps perfectly to

    //   the surface of the display panel. This is usually true for touchscreens.

    // - In POINTER mode, we cannot assume that the display and the touch device have the same

    //   aspect ratio, since it is likely to be untrue for devices like external drawing tablets.

    //   In this case, we used a fixed scale so that 1) we use the same scale across both the x and

    //   y axes to ensure the mapping does not stretch gestures, and 2) the entire region of the

    //   display can be reached by the touch device.

    // - From this point onward, we are no longer in the discrete space of the raw coordinates but

    //   are in the continuous space of the logical display.

    ui::Transform scaleRawToDisplay;

    const float xScale = static_cast<float>(mViewport.deviceWidth) / rotatedRawSize.width;

    const float yScale = static_cast<float>(mViewport.deviceHeight) / rotatedRawSize.height;

    if (mDeviceMode == DeviceMode::DIRECT) {

        scaleRawToDisplay.set(xScale, 0, 0, yScale);

    } else if (mDeviceMode == DeviceMode::POINTER) {

        const float fixedScale = std::max(xScale, yScale);

        scaleRawToDisplay.set(fixedScale, 0, 0, fixedScale);

    } else {

        LOG_ALWAYS_FATAL("computeInputTransform can only be used for DIRECT and POINTER modes");

    }

    // Step 5: Undo the display rotation to bring us back to the un-rotated display coordinate space

    // that InputReader uses.

    static void assignPointerIds(const RawState& last, RawState& current);

    // Compute input transforms for DIRECT and POINTER modes.

    void computeInputTransforms();

    void configureDeviceType();