[PATCH] win32u: Get DC size in set_map_mode() only if needed.

[Florian Will]

SetMapMode(.., MM_TEXT) is called a lot in common gdiplus use cases via
gdi_transform_acquire(). Querying the size and resolution can be
expensive, and is not needed in the MM_TEXT case, so skip it in that
case.

When running the "ZusiDisplay" ET423 diagnostic display, which uses
gdiplus heavily, this change increases the "indicator blinking speed"
from 0.6 per second to 1 per second and probably hits the FPS limit now.
Also, CPU usage of the ZusiDisplay.exe process goes down from ~75% to
~42% of one core according to "top", and wineserver CPU usage goes down
from ~48% to ~3%.

Signed-off-by: Florian Will 
---
 dlls/win32u/mapping.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/dlls/win32u/mapping.c b/dlls/win32u/mapping.c
index 6c20f50a302..b4122644dfe 100644
--- a/dlls/win32u/mapping.c
+++ b/dlls/win32u/mapping.c
@@ -117,8 +117,12 @@ BOOL set_map_mode( DC *dc, int mode )
     if (mode == dc->attr->map_mode && (mode == MM_ISOTROPIC || mode == MM_ANISOTROPIC))
         return TRUE;

-    virtual_size = get_dc_virtual_size( dc );
-    virtual_res = get_dc_virtual_res( dc );
+    if (mode != MM_TEXT)
+    {
+        virtual_size = get_dc_virtual_size( dc );
+        virtual_res = get_dc_virtual_res( dc );
+    }
+
     switch (mode)
     {
     case MM_TEXT:

[Huw Davies]

On Tue, Nov 23, 2021 at 12:57:11PM +0100, Florian Will wrote:
> SetMapMode(.., MM_TEXT) is called a lot in common gdiplus use cases via
> gdi_transform_acquire(). Querying the size and resolution can be
> expensive, and is not needed in the MM_TEXT case, so skip it in that
> case.
>
> When running the "ZusiDisplay" ET423 diagnostic display, which uses
> gdiplus heavily, this change increases the "indicator blinking speed"
> from 0.6 per second to 1 per second and probably hits the FPS limit now.
> Also, CPU usage of the ZusiDisplay.exe process goes down from ~75% to
> ~42% of one core according to "top", and wineserver CPU usage goes down
> from ~48% to ~3%.
> Signed-off-by: Florian Will
>
> dlls/win32u/mapping.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/dlls/win32u/mapping.c b/dlls/win32u/mapping.c
> index 6c20f50a302..b4122644dfe 100644
> --- a/dlls/win32u/mapping.c
> +++ b/dlls/win32u/mapping.c
> @@ -117,8 +117,12 @@ BOOL set_map_mode( DC *dc, int mode )
>      if (mode == dc->attr->map_mode && (mode == MM_ISOTROPIC || mode == MM_ANISOTROPIC))
>          return TRUE;
> - virtual_size = get_dc_virtual_size( dc );
> - virtual_res = get_dc_virtual_res( dc );
> - if (mode != MM_TEXT)
> - {
> -
>    virtual_size = get_dc_virtual_size( dc );
> -
>    virtual_res = get_dc_virtual_res( dc );
> - }
> -

I've sent in something slightly less fragile as v2.

Thanks,
Huw.