SDL: Also send DPI change when expected resize.

From 9914e87faaa01a0a63f46ba97837b13d66355128 Mon Sep 17 00:00:00 2001
From: Pieter-Jan Briers <[EMAIL REDACTED]>
Date: Mon, 20 Jun 2022 12:53:10 +0200
Subject: [PATCH] Also send DPI change when expected resize.

---
 src/video/windows/SDL_windowsevents.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/video/windows/SDL_windowsevents.c b/src/video/windows/SDL_windowsevents.c
index f3ed588d8ab..6273a5a98db 100644
--- a/src/video/windows/SDL_windowsevents.c
+++ b/src/video/windows/SDL_windowsevents.c
@@ -1538,6 +1538,16 @@ WIN_WindowProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
                 /* This DPI change is coming from an explicit SetWindowPos call within SDL.
                    Assume all call sites are calculating the DPI-aware frame correctly, so
                    we don't need to do any further adjustment. */
+
+                if (data->videodata->dpi_scaling_enabled) {
+                    /* Update the cached DPI value for this window */
+                    data->scaling_dpi = newDPI;
+
+                    /* Send a SDL_WINDOWEVENT_SIZE_CHANGED saying that the client size (in dpi-scaled points) is unchanged.
+                       Renderers need to get this to know that the framebuffer size changed. */
+                    SDL_SendWindowEvent(data->window, SDL_WINDOWEVENT_SIZE_CHANGED, data->window->w, data->window->h);
+                }
+
 #ifdef HIGHDPI_DEBUG
                 SDL_Log("WM_DPICHANGED: Doing nothing, assuming window is already sized correctly");
 #endif