diff --git a/builtin/fstk/buttonbar.lua b/builtin/fstk/buttonbar.lua
index 64ac37f03..e53814751 100644
--- a/builtin/fstk/buttonbar.lua
+++ b/builtin/fstk/buttonbar.lua
@@ -28,10 +28,8 @@ local function buttonbar_formspec(self)
 	end
 
 	local formspec = {
-		"style_type[box;noclip=true]",
 		string.format("box[%f,%f;%f,%f;%s]", self.pos.x, self.pos.y, self.size.x,
 				self.size.y, self.bgcolor),
-		"style_type[box;noclip=false]",
 	}
 
 	local btn_size = self.size.y - 2*BASE_SPACING
@@ -71,7 +69,7 @@ local function buttonbar_formspec(self)
 			y = self.pos.y + BASE_SPACING,
 		}
 
-		table.insert(formspec, string.format("image_button[%f,%f;%f,%f;%s;%s;%s;true;false]tooltip[%s;%s]",
+		table.insert(formspec, string.format("image_button[%f,%f;%f,%f;%s;%s;%s;false;false]tooltip[%s;%s]",
 				btn_pos.x, btn_pos.y, btn_size, btn_size, btn.image, btn.name,
 				btn.caption, btn.name, btn.tooltip))
 	end
@@ -86,9 +84,6 @@ local function buttonbar_formspec(self)
 			y = self.pos.y + BASE_SPACING,
 		}
 
-		table.insert(formspec, string.format("style[%s,%s;noclip=true]",
-				self.btn_prev_name, self.btn_next_name))
-
 		table.insert(formspec, string.format("button[%f,%f;%f,%f;%s;<]",
 				btn_prev_pos.x, btn_prev_pos.y, get_scroll_btn_width(), btn_size,
 				self.btn_prev_name))
diff --git a/builtin/fstk/tabview.lua b/builtin/fstk/tabview.lua
index f09c4df2d..9f8889143 100644
--- a/builtin/fstk/tabview.lua
+++ b/builtin/fstk/tabview.lua
@@ -66,11 +66,22 @@ local function get_formspec(self)
 
 	local content, prepend = tab.get_formspec(self, tab.name, tab.tabdata, tab.tabsize)
 
-	local tsize = tab.tabsize or { width = self.width, height = self.height }
+	local ENABLE_TOUCH = core.settings:get_bool("enable_touch")
+
+	local orig_tsize = tab.tabsize or { width = self.width, height = self.height }
+	local tsize = { width = orig_tsize.width, height = orig_tsize.height }
+	tsize.height = tsize.height
+		+ TABHEADER_H -- tabheader included in formspec size
+		+ (ENABLE_TOUCH and GAMEBAR_OFFSET_TOUCH or GAMEBAR_OFFSET_DESKTOP)
+		+ GAMEBAR_H -- gamebar included in formspec size
+
 	if self.parent == nil and not prepend then
 		prepend = string.format("size[%f,%f,%s]", tsize.width, tsize.height,
 				dump(self.fixed_size))
 
+		local anchor_pos = TABHEADER_H + orig_tsize.height / 2
+		prepend = prepend .. ("anchor[0.5,%f]"):format(anchor_pos / tsize.height)
+
 		if tab.formspec_version then
 			prepend = ("formspec_version[%d]"):format(tab.formspec_version) .. prepend
 		end
@@ -78,12 +89,15 @@ local function get_formspec(self)
 
 	local end_button_size = 0.75
 
-	local tab_header_size = { width = tsize.width, height = 0.85 }
+	local tab_header_size = { width = tsize.width, height = TABHEADER_H }
 	if self.end_button then
 		tab_header_size.width = tab_header_size.width - end_button_size - 0.1
 	end
 
-	local formspec = (prepend or "") .. self:tab_header(tab_header_size) .. content
+	local formspec = (prepend or "")
+	formspec = formspec .. ("bgcolor[;neither]container[0,%f]box[0,0;%f,%f;#0000008C]"):format(
+			TABHEADER_H, orig_tsize.width, orig_tsize.height)
+	formspec = formspec .. self:tab_header(tab_header_size) .. content
 
 	if self.end_button then
 		formspec = formspec ..
@@ -98,6 +112,8 @@ local function get_formspec(self)
 						self.end_button.name)
 	end
 
+	formspec = formspec .. "container_end[]"
+
 	return formspec
 end
 
diff --git a/builtin/mainmenu/init.lua b/builtin/mainmenu/init.lua
index 41885e298..dd35334c2 100644
--- a/builtin/mainmenu/init.lua
+++ b/builtin/mainmenu/init.lua
@@ -23,6 +23,13 @@ mt_color_dark_green = "#25C191"
 mt_color_orange  = "#FF8800"
 mt_color_red = "#FF3300"
 
+MAIN_TAB_W = 15.5
+MAIN_TAB_H = 7.1
+TABHEADER_H = 0.85
+GAMEBAR_H = 1.25
+GAMEBAR_OFFSET_DESKTOP = 0.375
+GAMEBAR_OFFSET_TOUCH = 0.15
+
 local menupath = core.get_mainmenu_path()
 local basepath = core.get_builtin_path()
 defaulttexturedir = core.get_texturepath_share() .. DIR_DELIM .. "base" ..
@@ -89,7 +96,7 @@ local function init_globals()
 	mm_game_theme.set_engine() -- This is just a fallback.
 
 	-- Create main tabview
-	local tv_main = tabview_create("maintab", {x = 15.5, y = 7.1}, {x = 0, y = 0})
+	local tv_main = tabview_create("maintab", {x = MAIN_TAB_W, y = MAIN_TAB_H}, {x = 0, y = 0})
 
 	tv_main:set_autosave_tab(true)
 	tv_main:add(tabs.local_game)
diff --git a/builtin/mainmenu/tab_local.lua b/builtin/mainmenu/tab_local.lua
index 7f46be213..f0a7255d7 100644
--- a/builtin/mainmenu/tab_local.lua
+++ b/builtin/mainmenu/tab_local.lua
@@ -92,10 +92,16 @@ function singleplayer_refresh_gamebar()
 		end
 	end
 
+	local ENABLE_TOUCH = core.settings:get_bool("enable_touch")
+
+	local gamebar_pos_y = MAIN_TAB_H
+		+ TABHEADER_H -- tabheader included in formspec size
+		+ (ENABLE_TOUCH and GAMEBAR_OFFSET_TOUCH or GAMEBAR_OFFSET_DESKTOP)
+
 	local btnbar = buttonbar_create(
 			"game_button_bar",
-			core.settings:get_bool("touch_gui") and {x = 0, y = 7.25} or {x = 0, y = 7.475},
-			{x = 15.5, y = 1.25},
+			{x = 0, y = gamebar_pos_y},
+			{x = MAIN_TAB_W, y = GAMEBAR_H},
 			"#000000",
 			game_buttonbar_button_handler)
 
diff --git a/doc/lua_api.md b/doc/lua_api.md
index 6989f3483..ea728cfbe 100644
--- a/doc/lua_api.md
+++ b/doc/lua_api.md
@@ -5580,8 +5580,8 @@ Utilities
       },
 
       -- Estimated maximum formspec size before Minetest will start shrinking the
-      -- formspec to fit. For a fullscreen formspec, use a size 10-20% larger than
-      -- this and `padding[-0.01,-0.01]`.
+      -- formspec to fit. For a fullscreen formspec, use this formspec size and
+      -- `padding[0,0]`. `bgcolor[;true]` is also recommended.
       max_formspec_size = {
           x = 20,
           y = 11.25
diff --git a/doc/menu_lua_api.md b/doc/menu_lua_api.md
index df14b859d..be63af904 100644
--- a/doc/menu_lua_api.md
+++ b/doc/menu_lua_api.md
@@ -253,8 +253,8 @@ GUI
       },
 
       -- Estimated maximum formspec size before Minetest will start shrinking the
-      -- formspec to fit. For a fullscreen formspec, use a size 10-20% larger than
-      -- this and `padding[-0.01,-0.01]`.
+      -- formspec to fit. For a fullscreen formspec, use this formspec size and
+      -- `padding[0,0]`. `bgcolor[;true]` is also recommended.
       max_formspec_size = {
           x = 20,
           y = 11.25
diff --git a/games/devtest/mods/testfullscreenfs/init.lua b/games/devtest/mods/testfullscreenfs/init.lua
index e1af3ae33..7abc7f817 100644
--- a/games/devtest/mods/testfullscreenfs/init.lua
+++ b/games/devtest/mods/testfullscreenfs/init.lua
@@ -1,18 +1,30 @@
-local function show_fullscreen_fs(name)
-	local window = minetest.get_player_window_information(name)
-	if not window then
-		return false, "Unable to get window info"
-	end
+local function window_info_equal(a, b)
+	return
+		-- size
+		a.size.x == b.size.x and a.size.y == b.size.y and
+		-- real_gui_scaling, real_hud_scaling
+		a.real_gui_scaling == b.real_gui_scaling and
+		a.real_hud_scaling == b.real_hud_scaling and
+		-- max_formspec_size
+		a.max_formspec_size.x == b.max_formspec_size.x and
+		a.max_formspec_size.y == b.max_formspec_size.y and
+		-- touch_controls
+		a.touch_controls == b.touch_controls
+end
 
+local last_window_info = {}
+
+local function show_fullscreen_fs(name, window)
 	print(dump(window))
 
-	local size = { x = window.max_formspec_size.x * 1.1, y = window.max_formspec_size.y * 1.1 }
+	local size = window.max_formspec_size
 	local touch_text = window.touch_controls and "Touch controls enabled" or
 			"Touch controls disabled"
 	local fs = {
 		"formspec_version[4]",
 		("size[%f,%f]"):format(size.x, size.y),
-		"padding[-0.01,-0.01]",
+		"padding[0,0]",
+		"bgcolor[;true]",
 		("button[%f,%f;1,1;%s;%s]"):format(0, 0, "tl", "TL"),
 		("button[%f,%f;1,1;%s;%s]"):format(size.x - 1, 0, "tr", "TR"),
 		("button[%f,%f;1,1;%s;%s]"):format(size.x - 1, size.y - 1, "br", "BR"),
@@ -23,10 +35,37 @@ local function show_fullscreen_fs(name)
 	}
 
 	minetest.show_formspec(name, "testfullscreenfs:fs", table.concat(fs))
-	return true, ("Calculated size of %f, %f"):format(size.x, size.y)
+	minetest.chat_send_player(name, ("Calculated size of %f, %f"):format(size.x, size.y))
+	last_window_info[name] = window
 end
 
-
 minetest.register_chatcommand("testfullscreenfs", {
-	func = show_fullscreen_fs,
+	func = function(name)
+		local window = minetest.get_player_window_information(name)
+		if not window then
+			return false, "Unable to get window info"
+		end
+
+		show_fullscreen_fs(name, window)
+		return true
+	end,
 })
+
+minetest.register_globalstep(function()
+	for name, last_window in pairs(last_window_info) do
+		local window = minetest.get_player_window_information(name)
+		if window and not window_info_equal(last_window, window) then
+			show_fullscreen_fs(name, window)
+		end
+	end
+end)
+
+minetest.register_on_player_receive_fields(function(player, formname, fields)
+	if formname == "testfullscreenfs:fs" and fields.quit then
+		last_window_info[player:get_player_name()] = nil
+	end
+end)
+
+minetest.register_on_leaveplayer(function(player)
+	last_window_info[player:get_player_name()] = nil
+end)
diff --git a/src/clientdynamicinfo.cpp b/src/clientdynamicinfo.cpp
index c206018f3..12bc23abd 100644
--- a/src/clientdynamicinfo.cpp
+++ b/src/clientdynamicinfo.cpp
@@ -23,6 +23,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 
 #include "settings.h"
 #include "client/renderingengine.h"
+#include "gui/guiFormSpecMenu.h"
 #include "gui/touchcontrols.h"
 
 ClientDynamicInfo ClientDynamicInfo::getCurrent()
@@ -37,19 +38,22 @@ ClientDynamicInfo ClientDynamicInfo::getCurrent()
 
     return {
         screen_size, real_gui_scaling, real_hud_scaling,
-        ClientDynamicInfo::calculateMaxFSSize(screen_size, gui_scaling),
+        ClientDynamicInfo::calculateMaxFSSize(screen_size, density, gui_scaling),
         touch_controls
     };
 }
 
-v2f32 ClientDynamicInfo::calculateMaxFSSize(v2u32 render_target_size, f32 gui_scaling)
+v2f32 ClientDynamicInfo::calculateMaxFSSize(v2u32 render_target_size, f32 density, f32 gui_scaling)
 {
-    f32 factor = (g_settings->getBool("touch_gui") ? 10 : 15) / gui_scaling;
-    f32 ratio = (f32)render_target_size.X / (f32)render_target_size.Y;
-    if (ratio < 1)
-        return { factor, factor / ratio };
-    else
-        return { factor * ratio, factor };
+	// must stay in sync with GUIFormSpecMenu::calculateImgsize
+
+    const double screen_dpi = density * 96;
+
+    // assume padding[0,0] since max_formspec_size is used for fullscreen formspecs
+	double prefer_imgsize = GUIFormSpecMenu::getImgsize(render_target_size,
+            screen_dpi, gui_scaling);
+    return v2f32(render_target_size.X / prefer_imgsize,
+            render_target_size.Y / prefer_imgsize);
 }
 
 #endif
diff --git a/src/clientdynamicinfo.h b/src/clientdynamicinfo.h
index 39faeeecc..c43fcb8d8 100644
--- a/src/clientdynamicinfo.h
+++ b/src/clientdynamicinfo.h
@@ -42,6 +42,6 @@ public:
 	static ClientDynamicInfo getCurrent();
 
 private:
-	static v2f32 calculateMaxFSSize(v2u32 render_target_size, f32 gui_scaling);
+	static v2f32 calculateMaxFSSize(v2u32 render_target_size, f32 density, f32 gui_scaling);
 #endif
 };
diff --git a/src/gui/guiFormSpecMenu.cpp b/src/gui/guiFormSpecMenu.cpp
index 8b572276c..0371c26f3 100644
--- a/src/gui/guiFormSpecMenu.cpp
+++ b/src/gui/guiFormSpecMenu.cpp
@@ -3133,58 +3133,7 @@ void GUIFormSpecMenu::regenerateGui(v2u32 screensize)
 			offset = v2s32(0,0);
 		}
 
-		const double gui_scaling = g_settings->getFloat("gui_scaling", 0.5f, 42.0f);
-		const double screen_dpi = RenderingEngine::getDisplayDensity() * 96;
-
-		double use_imgsize;
-		if (m_lock) {
-			// In fixed-size mode, inventory image size
-			// is 0.53 inch multiplied by the gui_scaling
-			// config parameter.  This magic size is chosen
-			// to make the main menu (15.5 inventory images
-			// wide, including border) just fit into the
-			// default window (800 pixels wide) at 96 DPI
-			// and default scaling (1.00).
-			use_imgsize = 0.5555 * screen_dpi * gui_scaling;
-		} else {
-			// Variables for the maximum imgsize that can fit in the screen.
-			double fitx_imgsize;
-			double fity_imgsize;
-
-			v2f padded_screensize(
-				mydata.screensize.X * (1.0f - mydata.padding.X * 2.0f),
-				mydata.screensize.Y * (1.0f - mydata.padding.Y * 2.0f)
-			);
-
-			if (mydata.real_coordinates) {
-				fitx_imgsize = padded_screensize.X / mydata.invsize.X;
-				fity_imgsize = padded_screensize.Y / mydata.invsize.Y;
-			} else {
-				// The maximum imgsize in the old coordinate system also needs to
-				// factor in padding and spacing along with 0.1 inventory slot spare
-				// and help text space, hence the magic numbers.
-				fitx_imgsize = padded_screensize.X /
-						((5.0 / 4.0) * (0.5 + mydata.invsize.X));
-				fity_imgsize = padded_screensize.Y /
-						((15.0 / 13.0) * (0.85 + mydata.invsize.Y));
-			}
-
-			s32 min_screen_dim = std::min(padded_screensize.X, padded_screensize.Y);
-
-			double prefer_imgsize;
-			if (g_settings->getBool("touch_gui")) {
-				// The preferred imgsize should be larger to accommodate the
-				// smaller screensize.
-				prefer_imgsize = min_screen_dim / 10 * gui_scaling;
-			} else {
-				// Desktop computers have more space, so try to fit 15 coordinates.
-				prefer_imgsize = min_screen_dim / 15 * gui_scaling;
-			}
-			// Try to use the preferred imgsize, but if that's bigger than the maximum
-			// size, use the maximum size.
-			use_imgsize = std::min(prefer_imgsize,
-					std::min(fitx_imgsize, fity_imgsize));
-		}
+		double use_imgsize = calculateImgsize(mydata);
 
 		// Everything else is scaled in proportion to the
 		// inventory image size.  The inventory slot spacing
@@ -5072,3 +5021,68 @@ std::array<StyleSpec, StyleSpec::NUM_STATES> GUIFormSpecMenu::getStyleForElement
 
 	return ret;
 }
+
+double GUIFormSpecMenu::getFixedImgsize(double screen_dpi, double gui_scaling)
+{
+	// In fixed-size mode, inventory image size
+	// is 0.53 inch multiplied by the gui_scaling
+	// config parameter.  This magic size is chosen
+	// to make the main menu (15.5 inventory images
+	// wide, including border) just fit into the
+	// default window (800 pixels wide) at 96 DPI
+	// and default scaling (1.00).
+	return 0.5555 * screen_dpi * gui_scaling;
+}
+
+double GUIFormSpecMenu::getImgsize(v2u32 avail_screensize, double screen_dpi, double gui_scaling)
+{
+	double fixed_imgsize = getFixedImgsize(screen_dpi, gui_scaling);
+
+	s32 min_screen_dim = std::min(avail_screensize.X, avail_screensize.Y);
+	double prefer_imgsize = min_screen_dim / 15 * gui_scaling;
+	// Use the available space more effectively on small windows/screens.
+	// This is especially important for mobile platforms.
+	prefer_imgsize = std::max(prefer_imgsize, fixed_imgsize);
+	return prefer_imgsize;
+}
+
+double GUIFormSpecMenu::calculateImgsize(const parserData &data)
+{
+	// must stay in sync with ClientDynamicInfo::calculateMaxFSSize
+
+    const double screen_dpi = RenderingEngine::getDisplayDensity() * 96;
+	const double gui_scaling = g_settings->getFloat("gui_scaling", 0.5f, 42.0f);
+
+	// Fixed-size mode
+	if (m_lock)
+		return getFixedImgsize(screen_dpi, gui_scaling);
+
+	// Variables for the maximum imgsize that can fit in the screen.
+	double fitx_imgsize;
+	double fity_imgsize;
+
+	v2f padded_screensize(
+		data.screensize.X * (1.0f - data.padding.X * 2.0f),
+		data.screensize.Y * (1.0f - data.padding.Y * 2.0f)
+	);
+
+	if (data.real_coordinates) {
+		fitx_imgsize = padded_screensize.X / data.invsize.X;
+		fity_imgsize = padded_screensize.Y / data.invsize.Y;
+	} else {
+		// The maximum imgsize in the old coordinate system also needs to
+		// factor in padding and spacing along with 0.1 inventory slot spare
+		// and help text space, hence the magic numbers.
+		fitx_imgsize = padded_screensize.X /
+				((5.0 / 4.0) * (0.5 + data.invsize.X));
+		fity_imgsize = padded_screensize.Y /
+				((15.0 / 13.0) * (0.85 + data.invsize.Y));
+	}
+
+	double prefer_imgsize = getImgsize(v2u32(padded_screensize.X, padded_screensize.Y),
+			screen_dpi, gui_scaling);
+
+	// Try to use the preferred imgsize, but if that's bigger than the maximum
+	// size, use the maximum size.
+	return std::min(prefer_imgsize, std::min(fitx_imgsize, fity_imgsize));
+}
diff --git a/src/gui/guiFormSpecMenu.h b/src/gui/guiFormSpecMenu.h
index 12add12e6..7c4be4301 100644
--- a/src/gui/guiFormSpecMenu.h
+++ b/src/gui/guiFormSpecMenu.h
@@ -296,6 +296,11 @@ public:
 	void getAndroidUIInput();
 #endif
 
+	// Returns the fixed formspec coordinate size for the given parameters.
+	static double getFixedImgsize(double screen_dpi, double gui_scaling);
+	// Returns the preferred non-fixed formspec coordinate size for the given parameters.
+	static double getImgsize(v2u32 avail_screensize, double screen_dpi, double gui_scaling);
+
 protected:
 	v2s32 getBasePos() const
 	{
@@ -514,6 +519,9 @@ private:
 
 	// used by getAbsoluteRect
 	s32 m_tabheader_upper_edge = 0;
+
+	// Determines the size (in pixels) of formspec coordinate units.
+	double calculateImgsize(const parserData &data);
 };
 
 class FormspecFormSource: public IFormSource