output: save and restore crtc upon (de)activation

The crtc is saved from kmscon_output_activate, and restored from
kmscon_output_deactivate.
This means that when the program exits, the screen is back to what it
was - we don't need to switch back VTs if we started the program from an
fbcon, etc.

Signed-off-by: David Herrmann <dh.herrmann@googlemail.com>

diff --git a/src/output.c b/src/output.c
index 6b05846..4804afa 100644 (file)
--- a/src/output.c
+++ b/src/output.c
@@ -72,6 +72,8 @@ struct kmscon_output {
        unsigned int cur_rb;
        struct render_buffer rb[2];
        GLuint fb;
+
+       drmModeCrtcPtr saved_crtc;
 };
 
 enum compositor_state {
@@ -561,6 +563,8 @@ static void destroy_rb(struct render_buffer *rb,
  * This activates the output in the given mode. This returns -EALREADY if the
  * output is already activated. To switch modes, deactivate and then reactivate
  * the output.
+ * When the output is activated, its previous screen contents and mode are
+ * saved, to be restored when the output is deactivated.
  * Returns 0 on success.
  * This does not work if the compositor is asleep.
  */
@@ -583,15 +587,16 @@ int kmscon_output_activate(struct kmscon_output *output,
                mode = output->modes;
 
        comp = output->comp;
+       output->saved_crtc = drmModeGetCrtc(comp->drm_fd, output->crtc_id);
 
        ret = init_rb(&output->rb[0], comp, &mode->info);
        if (ret)
-               return ret;
+               goto err_saved;
 
        ret = init_rb(&output->rb[1], comp, &mode->info);
        if (ret) {
                destroy_rb(&output->rb[0], comp);
-               return ret;
+               goto err_saved;
        }
 
        output->current = mode;
@@ -625,23 +630,38 @@ err_fb:
        destroy_rb(&output->rb[1], output->comp);
        output->active = 0;
        output->current = NULL;
+err_saved:
+       if (output->saved_crtc) {
+               drmModeFreeCrtc(output->saved_crtc);
+               output->saved_crtc = NULL;
+       }
+
        return ret;
 }
 
 /*
  * Deactivate the output. This does not disconnect the output so you can
  * reactivate this output again.
+ * When the output is deactivated, the screen contents and mode it had before
+ * it was activated are restored.
  */
 void kmscon_output_deactivate(struct kmscon_output *output)
 {
        if (!output || !output->active)
                return;
 
-       /*
-        * TODO: Do we need to reset the CRTC/connector here? We delete an
-        * active framebuffer here so the crtc will become blank, but instead
-        * the previous framebuffer should be restored.
-        */
+       if (output->saved_crtc) {
+               drmModeSetCrtc(output->comp->drm_fd,
+                                               output->saved_crtc->crtc_id,
+                                               output->saved_crtc->buffer_id,
+                                               output->saved_crtc->x,
+                                               output->saved_crtc->y,
+                                               &output->conn_id,
+                                               1,
+                                               &output->saved_crtc->mode);
+               drmModeFreeCrtc(output->saved_crtc);
+               output->saved_crtc = NULL;
+       }
 
        glBindFramebuffer(GL_FRAMEBUFFER, 0);
        glDeleteFramebuffers(1, &output->fb);