From 0ef475e57e76c48cef5c7787e1a37a458009d496 Mon Sep 17 00:00:00 2001
From: Piotr Krygier <everyonecancode@gmail.com>
Date: Mon, 25 Sep 2023 09:31:52 +0200
Subject: [PATCH] Add time function Updates to objects should not be done in
 frame by frame basis, but by time difference. This commit adds time diff
 function which can be used to tell how much time has passed since last frame.

---
 graphics/src/vulkan_base.c    |  8 ++++++--
 graphics/src/vulkan_commons.c | 25 ++++++++++++++++++++++++-
 graphics/src/vulkan_commons.h |  4 ++++
 3 files changed, 34 insertions(+), 3 deletions(-)

diff --git a/graphics/src/vulkan_base.c b/graphics/src/vulkan_base.c
index 2fa50232..89cd30e9 100644
--- a/graphics/src/vulkan_base.c
+++ b/graphics/src/vulkan_base.c
@@ -562,13 +562,13 @@ uint8_t init_vulkan()
     STATUS_CHECK(create_descriptors());
 
     STATUS_CHECK(create_sync_objects());
+
+    rse_init_time();
     return status;
 }
 
 void draw_frame()
 {
-    vkWaitForFences(g_vulkan_state.device, 1, &g_in_flight_fences[g_vulkan_state.current_frame], VK_TRUE, UINT64_MAX);
-
     uint32_t image_index = 0U;
     VkResult result = VK_FALSE;
     VkSubmitInfo submit_info = {};
@@ -578,6 +578,10 @@ void draw_frame()
     VkPresentInfoKHR present_info = {};
     VkSwapchainKHR swap_chains[1];
 
+    vkWaitForFences(g_vulkan_state.device, 1, &g_in_flight_fences[g_vulkan_state.current_frame], VK_TRUE, UINT64_MAX);
+
+    rse_update_time();
+
     result = vkAcquireNextImageKHR(g_vulkan_state.device, g_vulkan_state.swapchain, UINT64_MAX, g_image_available_semaphores[g_vulkan_state.current_frame],
                                             VK_NULL_HANDLE, &image_index);
 
diff --git a/graphics/src/vulkan_commons.c b/graphics/src/vulkan_commons.c
index 5fee13a9..d0e261f2 100644
--- a/graphics/src/vulkan_commons.c
+++ b/graphics/src/vulkan_commons.c
@@ -1,3 +1,26 @@
 #include "vulkan_commons.h"
 
-struct rse_vulkan_state_t g_vulkan_state;
\ No newline at end of file
+#include <time.h>
+
+struct rse_vulkan_state_t g_vulkan_state;
+
+time_t g_last_frame_time;
+time_t g_this_frame_time;
+float g_float_delta_time;
+
+void rse_init_time()
+{
+    time(&g_last_frame_time);
+}
+
+void rse_update_time()
+{
+    g_last_frame_time = g_this_frame_time;
+    time(&g_this_frame_time);
+    g_float_delta_time = (float)difftime(g_this_frame_time, g_last_frame_time);
+}
+
+float inline rse_get_time_diff()
+{
+    return g_float_delta_time;
+}
\ No newline at end of file
diff --git a/graphics/src/vulkan_commons.h b/graphics/src/vulkan_commons.h
index c44acab1..aaf0e8aa 100644
--- a/graphics/src/vulkan_commons.h
+++ b/graphics/src/vulkan_commons.h
@@ -79,4 +79,8 @@ struct rse_instance_data_t {
     float scale;
 };
 
+void rse_init_time();
+void rse_update_time();
+float inline rse_get_time_diff();
+
 #endif /* RSE_VULKAN_GLOBAL_H */