imgui: Add support for sdl2 renderer (#1513)

+ allow to enable multiple backends

packages/i/imgui/port/xmake.lua

@@ -5,6 +5,7 @@ option("wchar32",      {showmenu = true,  default = false})
 option("freetype",     {showmenu = true,  default = false})
 option("glfw_opengl3", {showmenu = true,  default = false})
 option("glfw_vulkan",  {showmenu = true,  default = false})
+option("sdl2",         {showmenu = true,  default = false})
 option("user_config",  {showmenu = true,  default = nil, type = "string"})
 option("use_glad",     {showmenu = true,  default = false})
 
@@ -17,11 +18,15 @@ if has_config("glfw_opengl3") then
     if has_config("use_glad") then
         add_requires("glad")
     end
-elseif has_config("glfw_vulkan") then
+end
+if has_config("glfw_vulkan") then
     add_requires("glfw")
     add_requires("vulkansdk")
     add_requires("vulkan-headers")
 end
+if has_config("sdl2") then
+    add_requires("libsdl >=2.0.17")
+end
 
 target("imgui")
     set_kind("static")
@@ -52,12 +57,20 @@ target("imgui")
         else
             add_headerfiles("backends/imgui_impl_opengl3_loader.h")
         end
-    elseif has_config("glfw_vulkan") then
+    end
+
+    if has_config("glfw_vulkan") then
         add_files("backends/imgui_impl_vulkan.cpp", "backends/imgui_impl_glfw.cpp")
         add_headerfiles("backends/imgui_impl_vulkan.h", "backends/imgui_impl_glfw.h")
         add_packages("glfw")
         add_packages("vulkan-headers")
     end
+    
+    if has_config("sdl2") then
+        add_files("backends/imgui_impl_sdl.cpp", "backends/imgui_impl_sdlrenderer.cpp")
+        add_headerfiles("backends/imgui_impl_sdl.h", "backends/imgui_impl_sdlrenderer.h")
+        add_packages("libsdl")
+    end
 
     if has_config("user_config") then
         local user_config = get_config("user_config")

packages/i/imgui/xmake.lua

@@ -24,8 +24,9 @@ package("imgui")
     add_versions("v1.75", "1023227fae4cf9c8032f56afcaea8902e9bfaad6d9094d6e48fb8f3903c7b866")
 
     add_configs("user_config", {description = "Use user config (disables test!)", default = nil, type = "string"})
-    add_configs("glfw_opengl3", {description = "Use glfw+opengl3 as backend", default = false, type = "boolean"})
-    add_configs("glfw_vulkan", {description = "Use glfw+vulkan as backend", default = false, type = "boolean"})
+    add_configs("glfw_opengl3", {description = "Enable glfw+opengl3 backend", default = false, type = "boolean"})
+    add_configs("glfw_vulkan", {description = "Enable glfw+vulkan backend", default = false, type = "boolean"})
+    add_configs("sdl2", {description = "Enable sdl2 backend", default = false, type = "boolean"})
     add_configs("wchar32", {description = "Use 32-bit for ImWchar (default is 16-bit)", default = false, type = "boolean"})
     add_configs("freetype", {description = "Use FreeType to build and rasterize the font atlas", default = false, type = "boolean"})
 
@@ -45,9 +46,13 @@ package("imgui")
                 package:add("defines", "IMGUI_IMPL_OPENGL_LOADER_GLAD")
             end
             package:add("deps", "glfw")
-        elseif package:config("glfw_vulkan") then
+        end
+        if package:config("glfw_vulkan") then
             package:add("deps", "glfw")
         end
+        if package:config("sdl2") then
+            package:add("deps", "libsdl >=2.0.17")
+        end
         if package:version_str():find("-docking", 1, true) then
             package:set("urls", {"https://github.com/ocornut/imgui.git"})
         end
@@ -59,6 +64,7 @@ package("imgui")
             freetype     = package:config("freetype"),
             glfw_opengl3 = package:config("glfw_opengl3"),
             glfw_vulkan  = package:config("glfw_vulkan"),
+            sdl2         = package:config("sdl2"),
             user_config  = package:config("user_config"),
             use_glad     = package:version():lt("1.84") -- this flag will be used if glfw_opengl3 is enabled
         }