Cleaned up handling of basic alpha setting

This does a few things:
* Refactored adjust_surface_alpha to use SDL_SetSurfaceAlphaMod
* Made all uses of the legacy SDL_SetAlpha use adjust_surface_alpha
* Made adjust_surface_alpha now take a non-const reference and perform the operation on the surface directly.

projectfiles/CodeBlocks/wesnoth.cbp

@@ -957,8 +957,6 @@
 		<Unit filename="../../src/scripting/plugins/context.hpp" />
 		<Unit filename="../../src/scripting/plugins/manager.cpp" />
 		<Unit filename="../../src/scripting/plugins/manager.hpp" />
-		<Unit filename="../../src/sdl/alpha.cpp" />
-		<Unit filename="../../src/sdl/alpha.hpp" />
 		<Unit filename="../../src/sdl/exception.cpp" />
 		<Unit filename="../../src/sdl/exception.hpp" />
 		<Unit filename="../../src/sdl/image.cpp" />

src/CMakeLists.txt

@@ -389,7 +389,6 @@ set_target_properties(wesnoth-lua
 ########### Helper libraries ###############
 
 set(wesnoth-sdl_SRC
-	sdl/alpha.cpp
 	sdl/exception.cpp
 	sdl/rect.cpp
 	sdl/image.cpp

src/SConscript

@@ -158,7 +158,6 @@ libcampaignd_sources = Split("""
 libcampaignd = env.Library("campaignd", libcampaignd_sources, OBJPREFIX = "campaignd_")
 
 libwesnoth_sdl_sources = Split("""
-    sdl/alpha.cpp
     sdl/exception.cpp
     sdl/image.cpp
     sdl/rect.cpp
@@ -690,7 +689,6 @@ test_utils_sources = Split("""
     """)
 
 wesmage_sources = Split("""
-    sdl/alpha.cpp
     sdl/utils.cpp
     sdl/window.cpp
     tools/dummy_video.cpp
@@ -742,7 +740,6 @@ test_sources.extend(test_env.Object("tests/test_config_cache.cpp"))
 test = test_env.WesnothProgram("test", test_sources +  [libtest_utils, libwesnoth_extras, libwesnoth_core, libwesnoth, libwesnoth_sdl, libwesnoth_extras], have_test_prereqs)
 
 create_images_sources = Split("""
-    sdl/alpha.cpp
     sdl/utils.cpp
     sdl/window.cpp
     tests/create_images.cpp

src/attack_prediction_display.cpp

@@ -23,7 +23,6 @@
 #include "language.hpp"
 #include "marked-up_text.hpp"
 #include "resources.hpp"
-#include "sdl/alpha.hpp"
 #include "units/unit.hpp"
 #include "units/abilities.hpp"
 
@@ -431,7 +430,7 @@ void battle_prediction_pane::get_hp_distrib_surface(const std::vector<std::pair<
 	surf = create_neutral_surface(width, height);
 
 	// Disable alpha channel to avoid problem with sdl_blit
-	SDL_SetAlpha(surf, 0, SDL_ALPHA_OPAQUE);
+	adjust_surface_alpha(surf, SDL_ALPHA_OPAQUE);
 
 	SDL_Rect clip_rect = sdl::create_rect(0, 0, width, height);
 	Uint32 grey_color = SDL_MapRGBA(surf->format, 0xb7, 0xc1, 0xc1, SDL_ALPHA_OPAQUE);

src/display.cpp

@@ -1758,7 +1758,7 @@ void display::render_image(int x, int y, const display::tdrawing_layer drawing_l
 	//} else if(alpha != 1.0 && blendto != 0) {
 	//	surf.assign(blend_surface(surf,1.0-alpha,blendto));
 	} else if(alpha != ftofxp(1.0)) {
-		surf = adjust_surface_alpha(surf, alpha, false);
+		adjust_surface_alpha(surf, alpha);
 	}
 
 	if(surf == nullptr) {

src/editor/action/mouse/mouse_action.cpp

@@ -183,7 +183,7 @@ void mouse_action::set_terrain_mouse_overlay(editor_display& disp, const t_trans
 	image = mask_surface(image, image::get_hexmask());
 
 	// Add the alpha factor
-	image = adjust_surface_alpha(image, alpha);
+	adjust_surface_alpha(image, alpha);
 
 	// scale the image
 	const int zoom = disp.hex_size();
@@ -344,7 +344,8 @@ void mouse_action_paste::set_mouse_overlay(editor_display& disp)
 	int zoom = static_cast<int>(size * disp.get_zoom_factor());
 
 	// Add the alpha factor and scale the image
-	image = scale_surface(adjust_surface_alpha(image, alpha), zoom, zoom);
+	adjust_surface_alpha(image, alpha);
+	image = scale_surface(image, zoom, zoom);
 	disp.set_mouseover_hex_overlay(image);
 }
 
@@ -399,7 +400,7 @@ editor_action* mouse_action_starting_position::up_left(editor_display& disp, int
 		return nullptr;
 	}
 	auto player_starting_at_hex = disp.map().is_starting_position(hex);
-	 
+
 	if (has_ctrl_modifier()) {
 		if (player_starting_at_hex) {
 			location_palette_.add_item(*player_starting_at_hex);
@@ -461,7 +462,8 @@ void mouse_action_starting_position::set_mouse_overlay(editor_display& disp)
 	int zoom = static_cast<int>(size * disp.get_zoom_factor());
 
 	// Add the alpha factor and scale the image
-	image = scale_surface(adjust_surface_alpha(image, alpha), zoom, zoom);
+	adjust_surface_alpha(image, alpha);
+	image = scale_surface(image, zoom, zoom);
 	disp.set_mouseover_hex_overlay(image);
 }
 

src/editor/action/mouse/mouse_action_item.cpp

@@ -244,7 +244,8 @@ void mouse_action_item::set_item_mouse_overlay(editor_display& disp, const overl
 	int zoom = static_cast<int>(size * disp.get_zoom_factor());
 
 	// Add the alpha factor and scale the image
-	image = scale_surface(adjust_surface_alpha(image, alpha), zoom, zoom);
+	adjust_surface_alpha(image, alpha);
+	image = scale_surface(image, zoom, zoom);
 	disp.set_mouseover_hex_overlay(image);
 }
 

src/editor/action/mouse/mouse_action_map_label.cpp

@@ -121,7 +121,8 @@ void mouse_action_map_label::set_mouse_overlay(editor_display& disp)
 	int zoom = static_cast<int>(size * disp.get_zoom_factor());
 
 	// Add the alpha factor and scale the image
-	image = scale_surface(adjust_surface_alpha(image, alpha), zoom, zoom);
+	adjust_surface_alpha(image, alpha);
+	image = scale_surface(image, zoom, zoom);
 	disp.set_mouseover_hex_overlay(image);
 }
 

src/editor/action/mouse/mouse_action_select.cpp

@@ -70,7 +70,8 @@ void mouse_action_select::set_mouse_overlay(editor_display& disp)
 	int zoom = static_cast<int>(size * disp.get_zoom_factor());
 
 	// Add the alpha factor and scale the image
-	image = scale_surface(adjust_surface_alpha(image, alpha), zoom, zoom);
+	adjust_surface_alpha(image, alpha);
+	image = scale_surface(image, zoom, zoom);
 	disp.set_mouseover_hex_overlay(image);
 }
 

src/editor/action/mouse/mouse_action_unit.cpp

@@ -244,7 +244,8 @@ void mouse_action_unit::set_unit_mouse_overlay(editor_display& disp, const unit_
 	int zoom = static_cast<int>(size * disp.get_zoom_factor());
 
 	// Add the alpha factor and scale the image
-	image = scale_surface(adjust_surface_alpha(image, alpha), zoom, zoom);
+	adjust_surface_alpha(image, alpha);
+	image = scale_surface(image, zoom, zoom);
 	disp.set_mouseover_hex_overlay(image);
 }
 

src/editor/action/mouse/mouse_action_village.cpp

@@ -52,7 +52,8 @@ void mouse_action_village::set_mouse_overlay(editor_display& disp)
 	int zoom = static_cast<int>(size * disp.get_zoom_factor());
 
 	// Add the alpha factor and scale the image
-	image = scale_surface(adjust_surface_alpha(image, alpha), zoom, zoom);
+	adjust_surface_alpha(image, alpha);
+	image = scale_surface(image, zoom, zoom);
 	disp.set_mouseover_hex_overlay(image);
 }
 

src/editor/palette/tristate_button.cpp

@@ -24,7 +24,6 @@
 #include "log.hpp"
 #include "marked-up_text.hpp"
 #include "serialization/string_utils.hpp"
-#include "sdl/alpha.hpp"
 #include "sound.hpp"
 #include "video.hpp"
 #include "wml_separators.hpp"
@@ -252,8 +251,8 @@ void tristate_button::draw_contents() {
 	}
 
 //  TODO for later reference
-//	SDL_SetAlpha(nbase, SDL_SRCALPHA, SDL_ALPHA_OPAQUE);
-//	SDL_SetAlpha(image, 0, 0);
+//	adjust_surface_alpha(nbase, SDL_ALPHA_OPAQUE);
+//	adjust_surface_alpha(image, SDL_ALPHA_TRANSPARENT);
 //
 //	TODO might be needed.
 	bg_restore();

src/floating_label.cpp

@@ -23,8 +23,6 @@
 #include <set>
 #include <stack>
 
-#include "sdl/alpha.hpp"
-
 static lg::log_domain log_font("font");
 #define DBG_FT LOG_STREAM(debug, log_font)
 #define LOG_FT LOG_STREAM(info, log_font)
@@ -119,10 +117,10 @@ sdl::timage floating_label::create_image()
 			// dark background will darken the anti-aliased part.
 			// This 1.13 value seems to restore the brightness of version 1.4
 			// (where the text was blitted directly on screen)
-			foreground = adjust_surface_alpha(foreground, ftofxp(1.13), false);
+			adjust_surface_alpha(foreground, ftofxp(1.13));
 
 			SDL_Rect r = sdl::create_rect( border_, border_, 0, 0);
-			SDL_SetAlpha(foreground,SDL_SRCALPHA,SDL_ALPHA_OPAQUE);
+			adjust_surface_alpha(foreground, SDL_ALPHA_OPAQUE);
 			blit_surface(foreground, nullptr, background, &r);
 
 			img_ = sdl::timage(background);
@@ -141,7 +139,7 @@ sdl::timage floating_label::create_image()
 				img_ = sdl::timage(foreground);
 				return img_;
 			}
-			SDL_SetAlpha(foreground,SDL_SRCALPHA,SDL_ALPHA_OPAQUE);
+			adjust_surface_alpha(foreground, SDL_ALPHA_OPAQUE);
 			blit_surface(foreground, nullptr, background, &r);
 			img_ = sdl::timage(background);
 		}
@@ -192,16 +190,16 @@ surface floating_label::create_surface()
 			// dark background will darken the anti-aliased part.
 			// This 1.13 value seems to restore the brightness of version 1.4
 			// (where the text was blitted directly on screen)
-			foreground = adjust_surface_alpha(foreground, ftofxp(1.13), false);
+			adjust_surface_alpha(foreground, ftofxp(1.13));
 
 			SDL_Rect r = sdl::create_rect( border_, border_, 0, 0);
-			SDL_SetAlpha(foreground,SDL_SRCALPHA,SDL_ALPHA_OPAQUE);
+			adjust_surface_alpha(foreground, SDL_ALPHA_OPAQUE);
 			blit_surface(foreground, nullptr, background, &r);
 
 			surf_ = create_optimized_surface(background);
 			// RLE compression seems less efficient for big semi-transparent area
 			// so, remove it for this case, but keep the optimized display format
-			SDL_SetAlpha(surf_,SDL_SRCALPHA,SDL_ALPHA_OPAQUE);
+			adjust_surface_alpha(surf_, SDL_ALPHA_OPAQUE);
 		}
 		else {
 			// background is blurred shadow of the text
@@ -217,7 +215,7 @@ surface floating_label::create_surface()
 				surf_ = create_optimized_surface(foreground);
 				return surf_;
 			}
-			SDL_SetAlpha(foreground,SDL_SRCALPHA,SDL_ALPHA_OPAQUE);
+			adjust_surface_alpha(foreground, SDL_ALPHA_OPAQUE);
 			blit_surface(foreground, nullptr, background, &r);
 			surf_ = create_optimized_surface(background);
 		}

src/font.cpp

@@ -25,7 +25,6 @@
 #include "marked-up_text.hpp"
 #include "text.hpp"
 #include "tooltips.hpp"
-#include "sdl/alpha.hpp"
 #include "sdl/rect.hpp"
 #include "serialization/parser.hpp"
 #include "serialization/preprocessor.hpp"
@@ -853,7 +852,7 @@ static surface render_text(const std::string& text, int fontsize, const SDL_Colo
 		return surface();
 	} else if (surfaces.size() == 1 && surfaces.front().size() == 1) {
 		surface surf = surfaces.front().front();
-		SDL_SetAlpha(surf, SDL_SRCALPHA | SDL_RLEACCEL, SDL_ALPHA_OPAQUE);
+		adjust_surface_alpha(surf, SDL_ALPHA_OPAQUE);
 		return surf;
 	} else {
 
@@ -862,14 +861,14 @@ static surface render_text(const std::string& text, int fontsize, const SDL_Colo
 			return res;
 
 		size_t ypos = 0;
-		for(std::vector< std::vector<surface> >::const_iterator i = surfaces.begin(),
+		for(std::vector< std::vector<surface> >::iterator i = surfaces.begin(),
 		    i_end = surfaces.end(); i != i_end; ++i) {
 			size_t xpos = 0;
 			size_t height = 0;
 
-			for(std::vector<surface>::const_iterator j = i->begin(),
+			for(std::vector<surface>::iterator j = i->begin(),
 					j_end = i->end(); j != j_end; ++j) {
-				SDL_SetAlpha(*j, 0, 0); // direct blit without alpha blending
+				adjust_surface_alpha(*j, SDL_ALPHA_TRANSPARENT); // direct blit without alpha blending
 				SDL_Rect dstrect = sdl::create_rect(xpos, ypos, 0, 0);
 				sdl_blit(*j, nullptr, res, &dstrect);
 				xpos += (*j)->w;

src/game_display.cpp

@@ -118,8 +118,8 @@ void game_display::new_turn()
 		const time_of_day& old_tod = tod_manager_->get_previous_time_of_day();
 
 		if(old_tod.image_mask != tod.image_mask) {
-			const surface old_mask(image::get_image(old_tod.image_mask,image::SCALED_TO_HEX));
-			const surface new_mask(image::get_image(tod.image_mask,image::SCALED_TO_HEX));
+			surface old_mask(image::get_image(old_tod.image_mask,image::SCALED_TO_HEX));
+			surface new_mask(image::get_image(tod.image_mask,image::SCALED_TO_HEX));
 
 			const int niterations = static_cast<int>(10/turbo_speed());
 			const int frame_time = 30;
@@ -139,12 +139,14 @@ void game_display::new_turn()
 #else
 				if(old_mask != nullptr) {
 					const fixed_t proportion = ftofxp(1.0) - fxpdiv(i,niterations);
-					tod_hex_mask1.assign(adjust_surface_alpha(old_mask,proportion));
+					adjust_surface_alpha(old_mask, proportion);
+					tod_hex_mask1.assign(old_mask);
 				}
 
 				if(new_mask != nullptr) {
 					const fixed_t proportion = fxpdiv(i,niterations);
-					tod_hex_mask2.assign(adjust_surface_alpha(new_mask,proportion));
+					adjust_surface_alpha(new_mask, proportion);
+					tod_hex_mask2.assign(new_mask);
 				}
 #endif
 

src/image_modifications.cpp

@@ -19,7 +19,6 @@
 #include "image.hpp"
 #include "image_modifications.hpp"
 #include "log.hpp"
-#include "sdl/alpha.hpp"
 #include "serialization/string_utils.hpp"
 
 #include <map>
@@ -224,8 +223,7 @@ surface wipe_alpha_modification::operator()(const surface& src) const
 
 surface adjust_alpha_modification::operator()(const surface & src) const
 {
-	return adjust_surface_alpha_formula(src, formula_);
-}
+	return adjust_surface_alpha_formula(src, formula_);}
 
 surface crop_modification::operator()(const surface& src) const
 {
@@ -397,7 +395,7 @@ std::pair<int,int> scale_exact_modification::calculate_size(const surface& src)
 		}
 		h = old_h;
 	}
-	
+
 	return std::make_pair(w, h);
 }
 
@@ -420,7 +418,7 @@ std::pair<int,int> scale_into_modification::calculate_size(const surface& src) c
 		}
 		h = old_h;
 	}
-	
+
 	long double ratio = std::min(w / old_w, h / old_h);
 
 	return std::make_pair(old_w * ratio, old_h * ratio);
@@ -435,9 +433,12 @@ surface xbrz_modification::operator()(const surface& src) const
 	return scale_surface_xbrz(src, z_);
 }
 
+// TODO: make this take a non-const reference and don't construct the temp surface
 surface o_modification::operator()(const surface& src) const
 {
-	return adjust_surface_alpha(src, ftofxp(opacity_));
+	surface temp = src;
+	adjust_surface_alpha(temp, ftofxp(opacity_));
+	return temp;
 }
 
 float o_modification::get_opacity() const
@@ -523,13 +524,15 @@ surface darken_modification::operator()(const surface &src) const
 	return ret;
 }
 
+// TODO: make this take a non-const reference and don't construct the temp surface
 surface background_modification::operator()(const surface &src) const
 {
 	surface ret = make_neutral_surface(src);
 	SDL_FillRect(ret, nullptr, SDL_MapRGBA(ret->format, color_.r, color_.g,
 					    color_.b, color_.a));
-	SDL_SetAlpha(src, SDL_SRCALPHA, SDL_ALPHA_OPAQUE);
-	blit_surface(src, nullptr, ret, nullptr);
+    surface temp = src;
+	adjust_surface_alpha(temp, SDL_ALPHA_OPAQUE);
+	blit_surface(temp, nullptr, ret, nullptr);
 	return ret;
 }
 

src/sdl/alpha.cpp

@@ -1,31 +0,0 @@
-/*
-   Copyright (C) 2014 - 2016 by Mark de Wever <koraq@xs4all.nl>
-   Part of the Battle for Wesnoth Project http://www.wesnoth.org/
-
-   This program is free software; you can redistribute it and/or modify
-   it under the terms of the GNU General Public License as published by
-   the Free Software Foundation; either version 2 of the License, or
-   (at your option) any later version.
-   This program is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY.
-
-   See the COPYING file for more details.
-*/
-
-#include "sdl/alpha.hpp"
-
-
-int SDL_SetAlpha(SDL_Surface* surface, Uint32 flag, Uint8 alpha)
-{
-	if(flag & SDL_SRCALPHA) {
-		// Need to specify the alpha blend mode if not setting alpha as opaque
-		int blendModeResult = SDL_SetSurfaceBlendMode (surface, SDL_BLENDMODE_BLEND);
-		if (blendModeResult != 0)
-			return blendModeResult;
-
-		return SDL_SetSurfaceAlphaMod(surface, alpha);
-	} else {
-		return SDL_SetSurfaceAlphaMod(surface, SDL_ALPHA_OPAQUE);
-	}
-}
-

src/sdl/alpha.hpp

@@ -1,33 +0,0 @@
-/*
-   Copyright (C) 2014 - 2016 by Mark de Wever <koraq@xs4all.nl>
-   Part of the Battle for Wesnoth Project http://www.wesnoth.org/
-
-   This program is free software; you can redistribute it and/or modify
-   it under the terms of the GNU General Public License as published by
-   the Free Software Foundation; either version 2 of the License, or
-   (at your option) any later version.
-   This program is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY.
-
-   See the COPYING file for more details.
-*/
-
-#ifndef SDL_ALPHA_HPP_INCLUDED
-#define SDL_ALPHA_HPP_INCLUDED
-
-/**
- * @file
- * Compatibility layer for using SDL 1.2 and 2.0.
- *
- * Emulates SDL_SetAlpha.
- */
-
-#include <SDL.h>
-
-
-#define SDL_SRCALPHA 0x00010000
-
-int SDL_SetAlpha(SDL_Surface* surface, Uint32 flag, Uint8 alpha);
-
-
-#endif

src/sdl/rect.cpp

@@ -13,7 +13,6 @@
 */
 
 #include "sdl/rect.hpp"
-#include "sdl/alpha.hpp"
 #include "sdl/utils.hpp"
 
 #ifdef SDL_GPU
@@ -94,9 +93,11 @@ void fill_rect_alpha(SDL_Rect &rect, Uint32 color, Uint8 alpha, surface target)
 		return;
 	}
 
+	SDL_SetSurfaceBlendMode (tmp, SDL_BLENDMODE_BLEND);
+
 	SDL_Rect r = {0,0,rect.w,rect.h};
 	sdl::fill_rect(tmp,&r,color);
-	SDL_SetAlpha(tmp,SDL_SRCALPHA,alpha);
+	adjust_surface_alpha(tmp, alpha);
 	sdl_blit(tmp,nullptr,target,&rect);
 }
 

src/sdl/utils.cpp

@@ -21,7 +21,6 @@
 #include "color_range.hpp"
 
 #include "sdl/utils.hpp"
-#include "sdl/alpha.hpp"
 #include "sdl/rect.hpp"
 
 #include "neon.hpp"
@@ -141,9 +140,9 @@ surface make_neutral_surface(const surface &surf)
 		return nullptr;
 	}
 
-	surface const result = SDL_ConvertSurface(surf,&get_neutral_pixel_format(),SDL_SWSURFACE);
+	surface result = SDL_ConvertSurface(surf,&get_neutral_pixel_format(),SDL_SWSURFACE);
 	if(result != nullptr) {
-		SDL_SetAlpha(result,SDL_SRCALPHA,SDL_ALPHA_OPAQUE);
+		adjust_surface_alpha(result, SDL_ALPHA_OPAQUE);
 	}
 
 	return result;
@@ -172,9 +171,11 @@ surface create_optimized_surface(const surface &surf)
 	if(surf == nullptr)
 		return nullptr;
 
-	SDL_SetAlpha(surf,SDL_SRCALPHA|SDL_RLEACCEL,SDL_ALPHA_OPAQUE);
+	surface temp = surf;
 
-	return surf;
+	adjust_surface_alpha(temp, SDL_ALPHA_OPAQUE);
+
+	return temp;
 }
 
 surface stretch_surface_horizontal(
@@ -1201,43 +1202,13 @@ surface brighten_image(const surface &surf, fixed_t amount, bool optimize)
 	return optimize ? create_optimized_surface(nsurf) : nsurf;
 }
 
-surface adjust_surface_alpha(const surface &surf, fixed_t amount, bool optimize)
+void adjust_surface_alpha(surface& surf, fixed_t amount)
 {
-	if(surf== nullptr) {
-		return nullptr;
+	if(surf == nullptr) {
+		return;
 	}
 
-	surface nsurf(make_neutral_surface(surf));
-
-	if(nsurf == nullptr) {
-		std::cerr << "could not make neutral surface...\n";
-		return nullptr;
-	}
-
-	{
-		surface_lock lock(nsurf);
-		Uint32* beg = lock.pixels();
-		Uint32* end = beg + nsurf->w*surf->h;
-
-		if (amount < 0) amount = 0;
-		while(beg != end) {
-			Uint8 alpha = (*beg) >> 24;
-
-			if(alpha) {
-				Uint8 r, g, b;
-				r = (*beg) >> 16;
-				g = (*beg) >> 8;
-				b = (*beg);
-
-				alpha = std::min<unsigned>(unsigned(fxpmult(alpha,amount)),255);
-				*beg = (alpha << 24) + (r << 16) + (g << 8) + b;
-			}
-
-			++beg;
-		}
-	}
-
-	return optimize ? create_optimized_surface(nsurf) : nsurf;
+	SDL_SetSurfaceAlphaMod(surf, Uint8(amount));
 }
 
 class pixel_callable : public game_logic::formula_callable {
@@ -1296,7 +1267,8 @@ surface adjust_surface_alpha_formula(const surface &surf, const std::string& for
 		return nullptr;
 	}
 
-	SDL_SetAlpha(nsurf.get(),SDL_SRCALPHA,SDL_ALPHA_OPAQUE);
+	adjust_surface_alpha(nsurf, SDL_ALPHA_OPAQUE);
+
 	{
 		surface_lock lock(nsurf);
 		Uint32* cur = lock.pixels();

src/sdl/utils.hpp

@@ -277,7 +277,7 @@ surface brighten_image(const surface &surf, fixed_t amount, bool optimize=true);
  */
 surface get_surface_portion(const surface &surf, SDL_Rect &rect);
 
-surface adjust_surface_alpha(const surface &surf, fixed_t amount, bool optimize=true);
+void adjust_surface_alpha(surface& surf, fixed_t amount);
 surface adjust_surface_alpha_add(const surface &surf, int amount, bool optimize=true);
 surface adjust_surface_alpha_formula(const surface &surf, const std::string& formula, bool optimize=true);
 

src/widgets/textbox.cpp

@@ -19,7 +19,6 @@
 #include "widgets/textbox.hpp"
 #include "desktop/clipboard.hpp"
 #include "log.hpp"
-#include "sdl/alpha.hpp"
 #include "sdl/rect.hpp"
 #include "serialization/string_utils.hpp"
 #include "video.hpp"
@@ -99,11 +98,11 @@ void textbox::append_text(const std::string& text, bool auto_scroll, const SDL_C
 	const bool is_at_bottom = get_position() == get_max_position();
 	const ucs4::string& wtext = unicode_cast<ucs4::string>(text);
 
-	const surface new_text = add_text_line(wtext, color);
+	surface new_text = add_text_line(wtext, color);
 	surface new_surface = create_compatible_surface(text_image_,std::max<size_t>(text_image_->w,new_text->w),text_image_->h+new_text->h);
 
-	SDL_SetAlpha(new_text.get(),0,0);
-	SDL_SetAlpha(text_image_.get(),0,0);
+	adjust_surface_alpha(new_text, SDL_ALPHA_TRANSPARENT);
+	adjust_surface_alpha(text_image_, SDL_ALPHA_TRANSPARENT);
 	SDL_SetSurfaceBlendMode(text_image_, SDL_BLENDMODE_NONE);
 	sdl_blit(text_image_,nullptr,new_surface,nullptr);
 	SDL_SetSurfaceBlendMode(text_image_, SDL_BLENDMODE_BLEND);
@@ -240,7 +239,8 @@ void textbox::draw_contents()
 			// while not changing any applicable non-grayscale AA. Actual colored text will
 			// not look as good, but this is not currently a concern since GUI1 textboxes
 			// are not used much nowadays, and they will eventually all go away.
-			sdl_blit(adjust_surface_alpha(text_image_, ftofxp(0.3)), &src, surf, &dest);
+			adjust_surface_alpha(text_image_, ftofxp(0.3));
+			sdl_blit(text_image_, &src, surf, &dest);
 		}
 	}