videoctrl: generate VBL interrupts.

devices/video/videoctrl.cpp

@@ -155,15 +155,33 @@ void VideoCtrlBase::start_refresh_task() {
     this->refresh_task_id = TimerManager::get_instance()->add_cyclic_timer(
         refresh_interval,
         [this]() {
+            // assert VBL interrupt
+            if (this->int_ctrl)
+                this->int_ctrl->ack_int(this->irq_id, 1);
             this->update_screen();
         }
     );
+
+    uint64_t vbl_duration = static_cast<uint64_t>(1.0f / ((double)(this->pixel_clock) /
+        hori_total / vert_blank) * NS_PER_SEC + 0.5);
+    this->vbl_end_task_id = TimerManager::get_instance()->add_cyclic_timer(
+        refresh_interval,
+        refresh_interval + vbl_duration,
+        [this]() {
+            // deassert VBL interrupt
+            if (this->int_ctrl)
+                this->int_ctrl->ack_int(this->irq_id, 0);
+        }
+    );
 }
 
 void VideoCtrlBase::stop_refresh_task() {
     if (this->refresh_task_id) {
         TimerManager::get_instance()->cancel_timer(this->refresh_task_id);
     }
+    if (this->vbl_end_task_id) {
+        TimerManager::get_instance()->cancel_timer(this->vbl_end_task_id);
+    }
 }
 
 void VideoCtrlBase::get_palette_colors(uint8_t index, uint8_t& r, uint8_t& g,

devices/video/videoctrl.h

@@ -25,6 +25,7 @@ along with this program.  If not, see <https://www.gnu.org/licenses/>.
 #define VIDEO_CTRL_H
 
 #include <core/hostevents.h>
+#include <devices/common/hwinterrupt.h>
 #include <SDL.h>
 
 #include <cinttypes>
@@ -66,6 +67,8 @@ protected:
     int         active_height;  // height of the visible display area
     int         hori_total = 0;
     int         vert_total = 0;
+    int         hori_blank = 0;
+    int         vert_blank = 0;
     int         pixel_depth;
     float       pixel_clock;
     float       refresh_rate;
@@ -76,6 +79,11 @@ protected:
     uint8_t*    fb_ptr;
     int         fb_pitch;
     uint32_t    refresh_task_id = 0;
+    uint32_t    vbl_end_task_id = 0;
+
+    // interrupt suff
+    InterruptCtrl* int_ctrl = nullptr;
+    uint32_t       irq_id   = 0;
 
     std::function<void(uint8_t *dst_buf, int dst_pitch)> convert_fb_cb;