[PATCH] drm/qxl: fix cursor position with non-zero hotspot

[John Keeping <john@metanate.com>]

The SPICE protocol considers the position of a cursor to be the location
of its active pixel on the display, so the cursor is drawn with its
top-left corner at "(x - hot_spot_x, y - hot_spot_y)" but the DRM cursor
position gives the location where the top-left corner should be drawn,
with the hotspot being a hint for drivers that need it.

This fixes the location of the window resize cursors when using Fluxbox
with the QXL DRM driver and both the QXL and modesetting X drivers.

Signed-off-by: John Keeping <john@metanate.com>
---
This comes from the discussion in the thread at [1].  My test
environment is using:

    - X.Org X Server 1.17.4
    - xf86-video-qxl 0.1.4
    - spice-gtk3 0.30

[1] http://lists.freedesktop.org/archives/dri-devel/2015-November/thread.html#94650

 drivers/gpu/drm/qxl/qxl_display.c | 13 +++++++++----
 drivers/gpu/drm/qxl/qxl_drv.h     |  2 ++
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/qxl/qxl_display.c b/drivers/gpu/drm/qxl/qxl_display.c
index 183aea1..5edebf4 100644
--- a/drivers/gpu/drm/qxl/qxl_display.c
+++ b/drivers/gpu/drm/qxl/qxl_display.c
@@ -375,10 +375,15 @@ static int qxl_crtc_cursor_set2(struct drm_crtc *crtc,
 
 	qxl_bo_kunmap(user_bo);
 
+	qcrtc->cur_x += qcrtc->hot_spot_x - hot_x;
+	qcrtc->cur_y += qcrtc->hot_spot_y - hot_y;
+	qcrtc->hot_spot_x = hot_x;
+	qcrtc->hot_spot_y = hot_y;
+
 	cmd = (struct qxl_cursor_cmd *)qxl_release_map(qdev, release);
 	cmd->type = QXL_CURSOR_SET;
-	cmd->u.set.position.x = qcrtc->cur_x;
-	cmd->u.set.position.y = qcrtc->cur_y;
+	cmd->u.set.position.x = qcrtc->cur_x + qcrtc->hot_spot_x;
+	cmd->u.set.position.y = qcrtc->cur_y + qcrtc->hot_spot_y;
 
 	cmd->u.set.shape = qxl_bo_physical_address(qdev, cursor_bo, 0);
 
@@ -441,8 +446,8 @@ static int qxl_crtc_cursor_move(struct drm_crtc *crtc,
 
 	cmd = (struct qxl_cursor_cmd *)qxl_release_map(qdev, release);
 	cmd->type = QXL_CURSOR_MOVE;
-	cmd->u.position.x = qcrtc->cur_x;
-	cmd->u.position.y = qcrtc->cur_y;
+	cmd->u.position.x = qcrtc->cur_x + qcrtc->hot_spot_x;
+	cmd->u.position.y = qcrtc->cur_y + qcrtc->hot_spot_y;
 	qxl_release_unmap(qdev, release, &cmd->release_info);
 
 	qxl_push_cursor_ring_release(qdev, release, QXL_CMD_CURSOR, false);
diff --git a/drivers/gpu/drm/qxl/qxl_drv.h b/drivers/gpu/drm/qxl/qxl_drv.h
index 01a8694..3ab9017 100644
--- a/drivers/gpu/drm/qxl/qxl_drv.h
+++ b/drivers/gpu/drm/qxl/qxl_drv.h
@@ -135,6 +135,8 @@ struct qxl_crtc {
 	int index;
 	int cur_x;
 	int cur_y;
+	int hot_spot_x;
+	int hot_spot_y;
 };
 
 struct qxl_output {
-- 
2.6.3.462.gbe2c914